A preschool teacher retires after years on the job, ready for the next phase in her life. Sadly, that life would be taken far too soon.

How did Nanette Krentel die? Did she try to rescue her pets and was overcome by smoke inhalation? Was it a suicide by fire? Or was the blaze intentionally set to cover up a murder?

Nanette grew up along the bayous of New Orleans. Her sister Kim says she was the life of the party in a city that knows how to celebrate.

"Nanette, she was a very sweet, caring person," said Kim Watson. "She had a little bit of a feisty side to her, but she was loyal, you know, she cared for her family and friends."

Friends like Lori Rando, her lifelong best friend from high school.

But the person who Nanette spent the most time with is the one who captured her heart, Stephen Krentel, a man who just happened to be married at the time they met.

"She walked in a store that I had owned at the time and applied for a job, and I hired her," Stephen Krentel tells Crime Watch Daily. "She balanced me and I balanced her. We were opposites in a lot of ways."

It didn't take long for these opposites to become one. Stephen divorced his wife and soon married Nanette. He joined the fire department, and Nanette went to work as a preschool teacher.

"Absolutely loved it, loved being with the kids, and was one of the most sought-after teachers in this area," said Stephen. "She has a huge heart, she has tremendous compassion for animals, she just was a good person all the way around."

And Nanette's father Dan Watson says that compassion for animals sometimes put her in harm's way.

"One time I was with her and she stopped at a post office, and a gentleman had left his dog in the vehicle and the windows were rolled up, and it was 100 degrees out. Nan said 'I'm going in and talk to him,'" Dan tells Crime Watch Daily. "She went in and I didn't know what was going to happen. I thought 'Uh-oh.' No, they came out and they were friends and he thanked her and said he wouldn't do it again."

So what better place to raise animals than the hundred-acre spread she shared with Stephen in Lacombe, Louisiana? She recently retired and found that life in the piney woods could allow her to enjoy her other hobby. She was also a gun enthusiast. She knew how to shoot and she was very comfortable with guns.

"It was something that we could walk out our back door and do on a routine basis, and she didn't go anywhere without at least one gun with her," said Stephen.

And Nanette had a lot of guns: for the house, the car and her purse. But despite what appeared to be a happy life, there were problems in the marriage.

"Her troubles varied, it just depended on the things that were going on, the influences in our life at the time," said Stephen.

Despite some troubles, rural life seemed to be good for the Krentels -- until the afternoon of July 14, 2017, when the fire consumed everything.

"I got a phone call from my cousin and he was telling me that my house was on fire," Stephen said. "At that second, I hung the phone up, ran out with my chief of training, we jumped in my department vehicle and started driving to the house. I was calling her cellphone, I was calling the house phone, but everything was going straight to voicemail."

Crime Watch Daily obtained footage of the moment when Stephen Krentel was rushing to the scene of his own home burning to the ground.

"We could actually see the smoke coming over the treetops, and we knew it was a fire of some type. I was just hoping it was the woods or something like that on fire," said Stephen. "When we got to a point that we could see the home, it was from one end to the other, it was fully involved."

What's it like being at the location? Is it uncomfortable for you? Is it a bad memory?

"It's not a bad memory because we lived out here for 17 years, and there's a lot of wonderful memories here, but it just hurts, it's empty, it just doesn't feel right, it doesn't feel like home right now, it just feels empty," said Stephen.

Stephen said when he arrived on the fire scene, his hopes were that Nanette made it out. But he suspected the worst.

"Right here where the garage was there were two garage doors on this side and the garage doors fell in, and that's when I knew that her car was here, my personal truck was here, and I had just walked off over there and just laid on the ground from there," Stephen tells Crime Watch Daily. "As soon as I saw the two of them coming over here to over there and walking straight to me, I knew they had found her at that time."

Your colleagues, your firefighter friends told you where she was?

"Yes, they told me where she was, and when the coroner got here that evening to recover her remains, I was over there still, and there was so many personnel out here that they made a wall of people standing shoulder to shoulder so that I couldn't see them move her," said Stephen.

The coroner takes Nanette's charred body to the morgue, and soon makes a shocking discovery: The fire didn't kill Nanette.

It was something even more ominous.

Nanette Krentel's friends and family were preparing for her funeral when they got news even more shocking than her death in the house fire. She was shot.

"The cause of death was a gunshot wound to the head, and the manner of death was a homicide," St. Tammany Parish, Louisiana Coroner Dr. Charles Preston said. "I am aware that the sheriff's office may have a different interpretation of the fact, but we feel that the evidence strongly supports the notion that she was dead before the fire started."

The corner said it clearly: It was homicide, not suicide. The fire didn't kill Nanette Krentel.

When you heard "murder," what went through your mind?

"I still can't fathom or understand how that even came to be," said Stephen Krentel. "I was under the impression that something caused the house to burn, everything from lightning to burning something on the stove, or something like that. That's all I could think that it could be."

"My response was 'I knew it, I knew it.' I knew somebody did this, she didn't just die in that fire," said Nanette's sister Kim Watson.

So now this shifts from a fire investigation into a homicide investigation. St. Tammany Parish Sheriff Randy Smith tells Crime Watch Daily it appears that the fire was ignited to cover up Nanette's murder.

"At this point, yes, the fire was intentionally set," said Sheriff Smith.

But it's not been classified as an arson just yet?

"No," said Smith. "They're waiting on evidence that was collected and sent off to the lab for analysis."

Investigators found a gun next to Nanette's body.

"We did locate a gun that we believed could have been used to kill Nanette," said Sheriff Smith. "That gun was sent off for ballistics testing, and unfortunately due to the hot temperatures of this fire, we weren't able to pinpoint whether the ballistics match the bullet that was discovered within her head. There is a strong possibility that that was the gun that killed Nanette."

The sheriff won't reveal the caliber of bullet nor the type of gun that killed Nanette Krentel because the case is still under investigation.

Lori Watson speculates that the gun was not Nanette's, and that someone might possibly have killed Nanette the night before the fire. She bases her theory on Nanette's social media activity.

"We were actually talking on Facebook, on the wall," said Lori Rando. "We were real time, just everything was fine. It was probably about 10:30 at night, it had been going on for a few hours. It just kind of abruptly stopped. Somebody has to walk away from their computer, or something along those lines, but it did stop."

But Sheriff Smith says that scenario is impossible and just didn't happen. He says he's got proof Nanette was alive just hours before the fire broke out after 2 p.m. They have video of Nanette Krentel at a McDonald's.

"We have video surveillance that puts her in that area, which was earlier on before her death and before the fire," said Sheriff Smith.

You can see it was her and not just someone in her car?

"We are very certain that it was her, not someone else in her car," said Smith.

We asked the sheriff to see the video, but he says because this is an active case he can't release it.

What about the security cameras Nanette and Stephen Krentel had throughout their property?

"Unfortunately due to the severe damage it caused from the fire, the hot fire, the video surveillance recorder and most of the cameras that were in place were destroyed," said Sheriff Smith. "We also sent that off to the FBI to get their expert analysis, but unfortunately it was too badly destroyed.

"Whoever did this, I believe, knew her, knew the layout of the residence, the location. I don't see this as a random act of violence," said Smith.

Not random -- intentionally set, the words from the sheriff. So the first person investigators looked at is the one person who knows everything about fires.

"Of course the chief, Stephen, was our first person of interest," said Smith.

The fire chief, Nanette's husband Stephen.

You would be a person of interest because you are the husband. It was a well-set fire, you are a fire chief.

"I was never offended or upset when the police were investigating me and looking at everything. That to me made perfect sense," said Stephen. "Statistically, I would be the individual that needed to be the primary focus, and I cooperated with everything."

They didn't ask you for a polygraph, but you volunteered to take one?

"I offered to do it immediately. We didn't hesitate, I went straight in," said Smith. "They gave it to me that day and came back an hour or so later and gave me the results. There were only three options: Either I did it, somebody else did it, or she had done it to herself, and I can go to sleep every night knowing I had nothing to do with this."

The sheriff tells us the results showed no deception. And Stephen had an ironclad alibi: he was at work at the fire station in Covington when the fire started, about 17 miles away from his house in Lacombe.

Has he been cleared?

"He has been cleared at this time," said Sheriff Smith. "Of course that could change during the course of this investigation, but right now we're pretty clear he was not there at the time of her death."

It's a mystery. Everyone seemed to love Nanette Krentel. But as the investigation ramps up, it's becoming painfully obvious that someone had it out for her.

Nanette Krentel had been killed, her house set ablaze, and police soon learned that in the weeks leading up to her murder, someone had threatened her life.

Seventeen days before she was shot to death and her house burned to the ground, Nanette Krentel emailed her father an image of a mystery man lurking outside her front gate.

"She said she was being followed," said Dan Watson. "She also said that she had found a knife and a cigarette butt on the property, and she said 'Somebody has come onto the property.'"

In her email Nanette wrote this caption: "This was the day I got out to get the mail and looked up and this man was walking towards me. He just looks creepy!"

The man is unidentified and nothing apparently came of it. Dan was worried about his daughter's safety living in the rural bayous of Louisiana, so she sent him pictures of her arsenal.

"She had one gun in her purse, one gun, a different gun, in her car, another gun in the house, plus she had a Remington 20-gauge home-defense shotgun, and I know there was an AR-15 because she said 'This is my baby,'" said Dan.

Best friend Lori Rando says Nanette amassed the firepower to protect her from someone a little closer to home: her brother-in-law, Stephen's brother, Brian Krentel.

"She never felt safe, not even in her own home," said Lori.

Because of her brother-in-law, she carried a gun around with her the entire time?

"Everywhere she went," said Lori.

Do you think he would harm you, harm Nanette?

"I did not believe it, but when something like this happens, you have to think that's a possibility," said Stephen Krentel. "Because if that's the case, he or anybody should pay for this."

Nanette revealed her fears about Brian in a series of Facebook exchanges with Lori, saying: "The night he got arrested he told Steve he was going to get out, kill us and then himself."

"We had many conversations via emails talking about Brian and how scared she was of him," said Lori. "He would threaten her, because I think he felt that she was kind of sticking her nose in his family business where it didn't belong."

Why would Nanette claim she felt threatened? Stephen says it could be because of an incident a few years before Nanette's death.

He asked you for help one day, but he was drinking and driving.

"He was drinking and the police wound up arresting him that evening, and he went to jail for about a year, and I know that he felt, because Nanette did go with me when we went to the scene that night, and he felt that we beared some responsibility for that, and he had a hard time forgiving us for that," said Stephen.

Brian Krentel has a long rap sheet with 36 arrests for petty crimes. So that, along with those alleged threats, made him a person of interest.

"He was a second person of interest, so we had to go back and follow up in our investigation to see where his whereabouts were," said Sheriff Smith. "And his alibi checked out, and he's still a person of interest, but not at this time."

That alibi was as ironclad as the jailhouse ankle bracelet he was wearing. Brian Krentel was under house arrest at his mother's home, and security video places him there the day of the murder.

Was he also home the night before?

"That is correct, we have information that we checked out his alibi, and he was present at that time," said Sheriff Smith.

The sheriff says Brian cooperated with investigators.

Has he ever come to you and said "Listen, I had nothing to do with this?"

"I really haven't asked," said Stephen. "I haven't asked him and we've never really discussed it. I believe in what the sheriff's office says, and if they could find a connection, they would."

Well Stephen may not have asked his brother. But that won't stop Crime Watch Daily from getting the answers straight from Brian Krentel. With his brother Stephen's help, we spoke to Brian on the phone.

So obviously you and your brother were persons of interest. You both ended up taking and passing polygraph tests. Did you volunteer, or how did that come about?

"I volunteered to take the test after they asked," said Brian Krentel.

OK, and you had no problem with that?

"Oh no, ma'am, no ma'am," said Brian.

So when you heard that this was a homicide and it was a murder, what went through your mind?

"Actually I couldn't believe it, you know," said Brian. "Just as I have known her, you know, why would anybody think of doing that, or why would they want to do that, you know? So it was a total shock"

What was going through your mind when they said "We're looking into you"?

"Actually it didn't really bother me, because I didn't have nothing to worry about, you know. I loved her," said Brian. "She was like a sister I didn't have, let's put it that way."

There was an email that Nanette said that she had been afraid of you, that maybe there were threats exchanged at one point. Do you remember an altercation or a fight?

"Oh, not with Nanette," said Brian. "Now, my brother and I might have had a fight. I've been fighting with him since I was born. But with Nan, I ain't never had a cross word, she ain't never had a cross word to me. It does shock me because I would think she would have came and asked me first if she had a problem with me."

The sheriff said that it's definitely not random. Whoever did this knew where they lived, knew of them. Who do you think? Do you have any theories?

"I would not have a clue," said Brian. "You know, it would be like snowing in Louisiana: It's a one-time thing, every now and then, you know."

Investigators are back at square one. The coroner says it wasn't suicide. Is there a clue detectives have overlooked?

Nanette Krentel was armed to the teeth. But that didn't save her from someone putting a bullet in her skull.

Your wife was a really good shooter and always carried a gun. Do you think she was caught off guard, could she see someone coming? What does your gut tell you about that day?

"I don't know what to think, because where she was found does not make sense," said Stephen Krentel.

Nanette's body was found in the master bedroom suite. She was shot before the blaze that destroyed the home she shared with her fire chief husband Stephen. Her precious pets, a dog and two cats, were reportedly shot as well.

"You know, we had 17 homicides here in our jurisdiction, in St. Tammany Parish, last year and this is the only one that we haven't solved yet," said Sheriff Randy Smith. "We just need that one piece, that one piece of information that we're still missing."

But that missing piece of the puzzle -- the piece that could solve this case -- went up in smoke.

"This fire, whoever set the fire knew what they were doing," said Sheriff Smith. "We don't have a motive to pinpoint to a certain individual. Again, I don't see it as a random act of violence, but it is a homicide that did occur, and that's how we're going to handle it."

"I have asked 'Why' a million times, and I cannot come up with a legitimate reason or logic to it at all," said Stephen Krentel.

Sheriff Smith cleared Stephen and his brother Brian as persons of interest, for now.

Nanette told her friend Lori Rando she was also afraid of Stephen's son Justin from a previous marriage.

"Justin was or is kind of a rebel child who doesn't necessarily feel that he needs to be held accountable for his actions," said Lori.

Did the stepson ever threaten Nanette?

"No, not to my knowledge," said Lori.

Nanette claimed on a Facebook posting to Lori: "The scary part is Justin is dangerous, has multiple guns."

Justin was out of state at the time of the fire, and there is no evidence he ever threatened her.

How was the relationship between her and your son?

"It was very good, especially the older he got," said Stephen.

Stephen shared a video of Nanette dancing with Justin at his wedding, and from all appearances everything seemed to be fine between stepmother and son. Remember, Stephen was married when he started dating Nanette. And apparently he was cheating on her too.

"It was the day before her birthday and we met for lunch and she told me that she thought Steve was having an affair, and she said it was someone from the firehouse, but it wasn't a fireman," said Lori. "I asked her why she thought this was going on or why she thought he was having an affair, and she said that he was spending just a little too much time at work, and when she was at the firehouse they seemed to be very, very close, like unusually close for co-workers."

Stephen tells Crime Watch Daily he came clean to Nanette about the affair long before her murder.

"She didn't find out in the last year or two, it's been at least a year or two since she found out about it," said Stephen.

"She said she was going to let it go," said Lori.

But Nanette's cousin Gina Watson wasn't going to let it go that easily. She says Nanette confided in her about the affair, and when Stephen admitted it to her, Gina says she confronted him.

"When he first told me that Nanette knew of the affair, he said that she approved of it 100 percent. Those were his words," said Gina. "And I stopped him right there and said 'I do not believe that. That's going a little too far.'"

Gina says there was something else that concerned her: Nanette was always ailing from some very mysterious injuries.

"She had a shoulder injury followed by a foot injury. I believe her knee was out at one point. Her hand, her wrist. And there was always kind of funny stories to go along with that," Gina tells Crime Watch Daily. "But one of them was they were painting and Stephen dropped a can of paint on her shoulder. I don't know how that would happen. Things that just didn't add up."

Were things in the marriage not as they may have appeared?

Did she mention anything about his moods changing? Was he controlling, abusive?

"I never felt that he was physically abusing her at the time," said Lori. "In retrospect, looking back on it, she seemed to be injured a lot. We would joke about it, she was really kind of clumsy."

Stephen Krentel vehemently denies any hint of alleged abuse, telling us Nanette's shoulder injury was a rotator cuff, and the injury to her foot was the result of dropping a can of wasp spray.

And despite his wandering eye, he tells Crime Watch Daily he was devoted to her, and she was to him, up until her final moments.

"She felt her job was to take care of me to the best of her abilities, and something as simple as every single day she put my clothes out for me, every morning whenever I was leaving to go somewhere, she walked me out, and it was no different that day," said Stephen.

What do you want most at this point?

"Answers," said Stephen. "I want to know what happened, and I want to see the individual have to face what they did."

Do you think that day will come?

"I do. I do," said Stephen. "I can't wait to look at that person, and just know who and why."

"Her smile, her face, when she would call me. She was always so upbeat. I would just like to see her one more time," said Nanette's father Dan Watson.

The sheriff is asking for anyone with information about the case to contact the City of New Orleans Crimestoppers at (504) 822-1111. You can also submit a tip anonymously to Crime Watch Daily.