A young Texas woman on the fast track to becoming a police officer, until a nasty fight with her boyfriend ends with him shot dead, and her holding the gun. Was it self-defense like she claims, or was it murder?

Claudia Esquivel was in love. She had just graduated from a law enforcement academy. But after a fight with her boyfriend, the police officer in training would find herself on the other side of the law.

On Father's Day weekend in 2014, at a popular restaurant in Galveston, Texas, 27-year-old Chris Chapa and his girlfriend, 22-year old Claudia Esquivel, are pulling double shifts.

But Chapa isn't just busy on this Father's Day. He's heartbroken. Four years earlier he lost a baby with his then-high school sweetheart.

"Christopher never really recovered from losing his daughter. It was something that sort of stuck with him," said Alana Holmes, Chapa's sister. "And so he had to work and he went into work with a very heavy heart, did his job the best that he could, but everyone could tell he just wasn't himself, and so managers let him go home early."

Chris leaves while his girlfriend, Claudia, remains behind at work. Claudia's not a cop yet, but well on her way once she passes her state exams.

Around 11 p.m., Claudia wraps up her shift at the restaurant and heads home to the apartment she shares with Chris. And tonight she's got a special surprise for him.

"She wanted to start cooking a crab boil at like 11 o'clock at night, whereas he just wanted to get ready for bed and start the next day," said Holmes. "Somewhere in that they started to get in an argument."

An argument that Chris's sister says began earlier that day when Chris sent a text to his former high school flame.

"Father's Day and Mother's Day were always hard times for Christopher and his high school sweetheart, and so they really didn't keep in touch a lot after they broke up, but those two days of the year they would kind of connect to each other through text message, just to kind of check in on one another, because they will always have that bond," said Holmes.

Chris's sister claims Claudia didn't like that bond. But that night Chris has plans of his own.

"While she was at work, Christopher and our youngest brother, had gotten together, had gone to dinner," said Holmes.

That ruined Claudia's crab boil surprise. While the meal is left to simmer down on the stove, Claudia's anger is just beginning to boil over.

"At some point Christopher was like, 'I'm done, I am going home, I am taking my stuff, I am going to my mom's house,' and he started collecting his belongings, and was like, 'This is the final straw.'

"At some point she got the gun and she held it to his head and pulled the trigger," said Holmes.

Chris collapses to the floor.

"It was one shot to the back of the head, and that was it. And instead of calling 911 to get help, she called her mother," said Holmes.

Several crucial minutes passed before Claudia's mother calls 911. She did not mention the shooting or request an ambulance. Her mother tells the 911 operator that Chris is hitting Claudia.

Galveston Police Detective Michelle Sollenberger is one of the first to arrive on scene and realizes this domestic disturbance call is actually a homicide.

"Chris was killed with a single gunshot wound to the head," said Sollenberger. "The entrance wound was behind his right ear towards the back of his head."

Chris Chapa lies bleeding to death with a mortal gunshot wound, and his girlfriend Claudia Esquivel is nowhere to be found.

"Officers contacted dispatch and dispatch did a little backtracking and contacted her mother," said Sollenberger. "Her mother then said this is where Claudia is. At that point she was in custody."

Claudia is escorted to the county jail by Major Crimes Detective Hector Dominguez Jr.

"She confirmed that she did want to talk about the case, so I took her back to the interview room," said Dominguez.

"It's basically another fight, like that consisted from throughout the whole day," Claudia says on recorded video of the interrogation. "I went through the trouble of making a crab steam pot and everything, right. Well, he gets in and just gives me this kiss and says 'Hey,' and kinda acts like nothing happened. And then it just starts escalating and escalating and I was like 'Whatever Chris.' So then he goes and gets in the shower, and I go in the shower and I go 'Really? You're just going to like bounce? You're not even going to eat dinner with me, I'm sitting here waiting for you.' And he goes '[----] you and your crab, I don't care,' acting all ugly, and I was like 'Fine, whatever,' I was like 'I'm just going to put it away.'"

Claudia puts the food away and takes out a gun.

"I grabbed it to scare him," Claudia says on the video. "I'm like 'Chris, I just want you to leave.'"

"I did, like, point it, and I was like 'Get out,' you know, and I'm going like this for him to get out of the door, to get out of there and quit causing all that ruckus, and he's like 'Oh, you're gonna shoot me.' He knows I'm not gonna shoot him. 'No, I wasn't going to shoot you.'"

But that's exactly what she did.

"It caught him right here on the side of the head, and I didn't even, you know when something happens so fast that you don't notice it, I thought the bullet just flew out. I didn't even know it hit him until I saw him hit the floor, because it took a minute before he just fell on the floor," Claudia says on the recording.

Claudia Esquivel claims it's a case of domestic violence that ended in an accidental shooting. She demonstrates the alleged assault to Detective Dominguez.

"He starts getting all rough and pushing me real hard and slamming me into the wall and stuff, and where I hit the side of the doorway and the wall and the door, and in the middle of that, arms go up and that's when the shot came out because my finger hit the trigger," Claudia says on the recording.

But Claudia maintains she only meant to intimidate Chris, not kill him.

"I took out the magazine," Claudia says on the video. "I unloaded it and an unloaded gun cannot hurt someone. It was supposed to be unloaded. I took the magazine out. An unloaded gun can't hurt someone.

"But I loved him. I would not kill him intentionally, or if I thought that I could have killed him, like honestly, I didn't think that there wasn't no bullet in the chamber," she says on the video.

While Claudia tells her side of the story at Galveston Police headquarters, investigators are collecting evidence at the crime scene that tells a very different story.

"The evidence didn't fit the pieces with her saying he was refusing to leave. She was trying to scare him into leaving. The evidence shows that he was fully dressed, his stuff was packed by the door and it looked like he was leaving, just maybe not fast enough for her taste," said Det. Sollenberger.

And that alleged domestic violence? Cops report no signs of a struggle or any defensive marks on Claudia's body.

"There was no reported history of domestic violence with the police department. We found no evidence that they had ever called the police on one another," said Sollenberger.

But they do learn about a prior physical incident between the couple, and the aggressor wasn't Chris.

"One particular incident that we learned about after the fact, Claudia had actually Tased Chris subsequent to an argument," said Sollenberger.

What about Claudia's claim she didn't know there was a bullet in the chamber?

"The first thing that you are taught in the police academy and in any firearms training is that the gun's always loaded. You know what you are pointing a gun at, and you don't point a gun at anything that you don't want to destroy," said Sollenberger.

Claudia Esquivel scored at the top of her firearms class at the police academy.

"I think that Claudia was enraged. I think she was mad. I think she was losing her boyfriend and I think that she was losing her boyfriend for possibly the last time. He might not come back this time. And I don't think she cared if there was a bullet in the chamber," said Sollenberger.

But was it an accidental shooting or murder?

"Whether she intended to pull the trigger and put a bullet through his head that night, I can't say," said Sollenbeger. "She's the only one that knows that."

But Chris and Claudia weren't alone in the apartment the night of the shooting. There was someone else: Claudia's 4-year-old son, who gave a statement that indicated he had witnessed everything.

"Not only did he see what happened, he was in the range of fire. The trajectory of the round actually traveled over where her son was laying on the couch, the blanket that he was covering up with while he was asleep prior to him being awoken by the arguing," said Det. Sollenberger. "The blanket actually had blood spatter on it."

And police investigators believe this little boy holds the answers to exactly what happened that terrible night.

The 4-year-old was interviewed by a child forensic interviewer. He says "Mommy" and Chris were fighting, and that she shot him. He described her bloody hands.

The boy draws a picture worth a thousand words, according to Detective Sollenberger.

According to cops, the boy describes Chris's blood stained T-shirt marked with his mother's bloody palm print seen in a police evidence photo. It's a detail only an eyewitness to the shooting would know.

"Chris died," said the boy. "He died. He can't get up. I'm finished. I don't want to color."

Claudia faces five years to life in prison for felony murder. Following closing arguments, jurors took just over six hours to return with a verdict.

"She was convicted and sentenced to 27 years in the prison system," said Galveston County Assistant District Attorney Beverly Armstrong.

Claudia Esquivel is up for parole in about 13 and a half years. But no matter how much time is served, the punishment is endless for both families.

Two young lives forever ruined over a petty fight, when the reality was:

"He wanted to marry her," said Chris Chapa's sister Alana Holmes.

"The last time we saw Christopher, he pulled us aside and talked about wanting to find the right ring, and he talked to my husband about, you know, 'I want to be a good husband, how do I do that, walk me through this, how do I figure this all out?' And he was really excited," said Holmes.

But instead of planning a wedding, one family plans a funeral and the other, prison visits.

Claudia Esquivel's young son now lives with her mother.