In Boise, Idaho a convicted murderer admits he's a killer -- but he says he had no choice.

From a drug store parking lot on a night in March 2011 comes a frantic 911 call. A violent showdown between two men vying for the attention of a blonde named Kandi. Cops arrive to find the woman hysterical and two men shot.

Kandi her husband Rob Hall and their two teenage daughters had just moved from California to Idaho, where they settled in Meridian, a quiet town at the foot of the majestic Rocky Mountains.

"Rob and Kandi Hall had been married for more than 15 years, and by a lot of accounts from their friends, were happy," said journalist Jamie Grey.

Rob worked as a computer guy at the local sheriff's department. Kandi was a paralegal. But the 40-year-old wife and mother was dealing with career struggles.

"She had recently lost a job at another law firm and so she was looking for somewhere to work," said Grey. "And that's how she met Emmett, was through being a paralegal."

Enter Emmett Corrigan, her soon-to-be boss. The rising legal star was boyishly handsome, cocky and ambitious, and at just 30 years old, he had just opened his own law practice.

"Emmett was, by all accounts, an up-and-coming kind of hotshot attorney," said Grey.

Corrigan appeared to lead a charmed life. Not only did he have a thriving career, he had a beautiful wife named Ashlee.

"They were married in a Mormon temple," said Jamie Grey. "By the time Ashlee is 30, she has five kids. Three girls and two boys."

The Corrigans were the picture of the squeaky-clean all-American family, and with Emmett's career on the rise, the future looked bright.

"Emmett was very driven, very enthusiastic," said Grey. "He was going to start taking more clients and be very successful."

And Kandi Hall was thrilled to be part of a vibrant new firm. But just as her professional life was making a turn for the better, her personal life was falling apart.

"She was having problems in her own marriage," said Grey. "Kandi at times had told people that Rob had been abusive toward her, that Rob had had an affair of his own."

Reeling from the news of her husband's infidelity, Kandi immersed herself in work, logging long hours at the office.

"She was in a place where she was looking for something else," said Grey.

And it seems Kandi found that something else in her dashing young boss, 10 years her junior.

"She was looking for something to be fulfilling to her," said Grey.

It wasn't long before Kandi and Emmett struck up a torrid affair, exchanging racy emails, spicy text messages and indulging in late-night rendezvous.

"They were having sex, apparently sometimes in the office," said Grey.

They tried to keep the relationship on the down-low, but soon the illicit affair became an open secret in the office.

"There were a number of coworkers who said they knew what was going, and clients also knew in some cases," said Grey.

And around that time, Ashlee, newly pregnant with her fifth child, noticed her husband becoming distant.

"I started thinking there's got to be another woman or something," Ashlee Birk tells Crime Watch Daily. "And the kids were starting to say 'Does he live here anymore? He's always at work.'"

Looking back, Ashlee remembers from the get-go she had uneasy feelings about Emmett's new "work wife."

"I said 'Emmett, I don't feel good about this one,' and he's like 'What do you mean? She's like a mother figure, like, she really believes in me, thinks that I'm going to be this great defense attorney,'" said Ashlee.

A mother figure who showered new mom Ashlee with gifts.

"She had sent me presents when the baby was born, for myself and the baby," said Ashlee.

Did you suspect that she had a thing for your husband, or that he may have had one for her?

"To be honest, I'd always be like 'She's like 40, he just turned 30, Ashlee, no, there's no way. I mean, you're 28 years old,'" said Ashlee.

But despite glaring red flags flying, Ashlee was convinced she was paranoid. When she made an appointment with a therapist, Emmett didn't show up.

"I ended up going by myself to this appointment, and I kind of sat in there asking him to fix me, like, 'I think I have issues,' and just started going off to this counselor, and by the end he was like, 'Ashlee, I feel like something's really wrong,'" said Ashlee.

Desperate to save her marriage, Ashlee planned a special night. She hoped it would finally convince her husband to stay home.

"It was kind of one of those days where I'm like, 'Today's it, I need him to see us, I'm going to have all the kids dressed to the nines, and the food and everything's gonna be perfect,' and he came home late, the food was cold, the kids were tired. He didn't eat a bite of my food," said Ashlee.

And like so many other nights, Emmett Corrigan picked a fight and then took off.

"Emmett came and said 'Hey, I'm going to run into Walgreens real quick, I got this cold, I'm gonna go and just get some medicine,' and I knew he was going to be gone a long time," said Ashlee.

But this night of deceit would change everything forever.

At the same time, just a few miles away, Kandi Hall tells her husband she's going to run a quick errand.

"Around 9 o'clock, Kandi, her car pulls into Walgreens and then Emmett's truck pulls into Walgreens, and Kandi says she got in Emmett's truck and then they went over to a gas station, filled up his truck with gas, and then they went to a nearby subdivision and they had sex in the truck," said Jamie Grey.

Love and lust clearly had Kandi and Emmett thinking no one knew -- until an odd coincidence changed everything. Kandi's daughter just happened to drive into the parking lot and notice her mom's empty car. Thinking it was strange, she called her dad.

"Well, Rob starts to wonder what's going on, and so Rob called Kandi's phone. Kandi answered the phone, and Emmett took the phone out of her hands," said Grey. "Kandi says that Emmett started to get threatening to Rob on the phone."

Robert heads to Walgreens, hellbent on finding his wife on a supposed errand.

Recorded on store surveillance video, Rob Hall parks his pickup truck, goes through the front door and roams the aisles looking for Kandi, never realizing Kandi and her lover Emmett were in Emmett's truck. Rob leaves the store and checks Kandi's parked BMW. Then strangely, he gets back into his own pickup truck, pulls out and parks again on the other side of Kandi's car.

His door is now just out of range of the store surveillance camera. But the unseen reality is that Rob has a gun.

"Rob Hall was armed with a gun that wasn't in a holster," said Jamie Grey. "Rob's gun was a gift from Kandi."

"In January, Rob sends Kandi a message that says basically, 'Good luck with Emmett. Once the honeymoon's over, karma's a bitch. I'll have the last laugh,'" said Jamie Grey.

In the Walgreens parking spot out of sight of surveillance cameras, next to Kandi's car, Rob lies in wait for his wife. Seventeen minutes later, Kandi and Emmett pull up and see Rob. What they don't know is he has a gun in his pocket and revenge on his mind.

"Kandi says at some point Rob provoked Emmett by saying 'Why don't you go home to your wife? You have five kids at home,' and that that set Emmett off," said Grey. "He pushed off of his truck and came at Rob. Kandi says she turned to leave and never saw what happened after that."

What happened? Someone was about to end up dead.

"Three gunshots. Emmett was shot in the chest and in the head, and Rob had a gunshot wound, a graze wound to his head," said Grey.

Kandi frantically calls 911. Minutes later help arrives. But Emmett Corrigan is quickly bleeding out in the arms of his lover Kandi Hall.

"Kandi says she then runs over to Emmett and is trying to put pressure on the wound, trying to figure out what happened. She saw Rob start to get up and she said she actually grabbed the gun and she threw it, she said she threw it like a bowling ball across the parking lot," said Grey.

It didn't matter. Emmett Corrigan died at the scene. Cops swarm Walgreens and arrest Rob Hall on the spot.

Across town, Emmett's wife Ashlee is about to get the worst unsuspected news imaginable.

"I open up the front door to these three strangers. They said 'There's been two shots of a gun. There's been an accident and an affair,'" Ashlee said.

Ashlee says what happens next is a blur.

"I remember looking around the room and everything just felt dizzy," said Ashlee. "I almost felt worthless, like three people all were making these choices that I had no idea were going to change the rest of my life."

Ashlee claims she had no idea about Emmett's affair until that fatal night.

"Just didn't make sense, and it was really a mix of emotions, wondering like, 'Why wasn't I enough? Why wasn't I enough for a husband who had a moment and a chance -- I begged him to stay home and fight for me, but instead he died fighting for someone else's wife," said Ashlee Birk.

Your husband died in the arms of another woman. How did that make you feel?

"Worthless. Ugly. Fat. I'd just had a baby. Just alone. Humiliated that the whole town heard the same news at the same time I did," said Ashlee.

At the hospital, Rob was treated for head wounds. Cops question him about the shooting.

"He was on morphine," said Jamie. "He's not being super lucid about what's going on. And he says 'Emmett shot me,' and then he says 'I shot,' and he stops, and he never says the end of the sentence."

What happened in that 17-minute gap between the time Rob waits for his wife by her car and Emmett winds up dead? The surveillance cameras didn't capture the moment, but there is one person who was there.

"There are no witnesses in the parking lot or customers or neighbors that saw someone pull a gun on someone else. And the only eyewitness is Kandi Hall," said Grey.

Cops soon bring her in for questioning. When detectives walk into the interrogation room, Kandi is hysterical.

Detective: "Please help us put this together. As best as we can we'll match statements with evidence. I mean, you know how police work goes."

Kandi Hall: "I know, I do it all day long."

Kandi tells detectives she went to Walgreens to pick up a prescription, and it's there she met up with Emmett, her boss. She says they are just friends, and needed to vent about her marital troubles.

Kandi: "Rob, my husband has, he has had a really hard time with me working with Emmett, Emmett being younger and you know, aggressive attorney, and I've been working with him for, since October."

Detective: "OK. Are you and Emmett involved in a romantic relationship?"

Kandi: "No."

Detective: "Have you ever been romantic with Emmett?"

Kandi: "No."

Detective: "OK, then let's say 'sexual.' Have you been sexual with him?"

Kandi: "No."

Kandi is obviously lying to detectives. Then she tells cops she got in Emmett's truck and they went to get gas, then she got a phone call.

Kandi: "So when I went and got gas at Fred Meyer with Emmett, and then we were driving back, my daughter called me and she said 'Mom, where are you?' And I told her I was with Michelle, and that is my best friend Michelle, because I didn't want to her know who I was with."

But Kandi leaves out one very important detail: After getting gas the couple headed to a secluded spot to have sex in Emmett's truck. Kandi's daughter sensed something fishy about her mom's "Michelle" story, and that's when she called her dad.

Kandi: "So then Rob calls, and he calls me and I pick up, and he's like 'What are you doing?' And I said 'I am out,' and he said 'Are you out with Emmett?' And I said 'I am,' and he said 'What are you doing?' and I said 'We're just talking,' and then Emmett goes 'Let me talk to him.' And then Emmett got really upset with Rob on the phone and said something like 'I'll -- I'll [----] break your head.'"

Kandi brushes off Emmett's threat and they drive back to Walgreens. But when they arrived, Rob was lying in wait.

Kandi: "Emmett got out of the truck and I got out and I stood there, and Rob came up and, and Emmett's a very aggressive man, he body-builds, so he's really pumped up all the time, and he got like this close up into Rob's face, and I remember, and I'm all 'Hey, knock it off, this is ridiculous.'"

Kandi says when she turned to leave, she heard the tragic sound ring out.

Kandi: "I hear 'pop-pop' and then 'pop,' and that's all I heard, and I turn around and both of them are laying on the ground. And then I ran over and I was like, I was pretty stunned at that point. I was like 'What in the world?' 'Cause I didn't even know what the 'pop-pop' was, it almost sounded like balloons popping.

"Emmett was kind of like on his, like this, and I, I didn't know what was going, and I just see all this blood gushing down his face, so I went over and I covered -- he had this wound on the top of his head and I'm covering it and I'm calling 911."

Kandi says she never actually saw the shooting. She then describes how her husband Rob stood up after being shot.

Kandi: "He was walking forward and, and I see him going down and I didn't even know what he was grabbing for because I didn't see it, 'cause it's little."

Rob was reaching for the gun. A terrified Kandi didn't know what her husband would do next.

Kandi: "So I grabbed it and I was holding onto his shirt because it looked like he was gonna fall, and I grabbed the gun, I go 'No, no, no, no,' and I'm all 'No, you need to sit down,' and I took it and I threw it in the street and that, that's all, and then he collapsed."

Kandi Hall is under the microscope. Her lover Emmett Corrigan is dead, and her scorned husband Rob Hall is now on trial for murder.

For weeks salacious secrets spilled out of the courtroom. The defense argued that Rob Hall was pushed to the brink of madness, a man consumed with jealousy over his wife's affair with her boss. But they claimed he shot in self-defense after an altercation with Corrigan.

"The defense really worked to paint Emmett as an aggressive sort of person who had a temper," said Jamie Grey.

The prosecution painted Rob Hall as a man obsessed, who hunted down his wife and her lover, first taking aim at Emmett, then turning the gun on himself.

"One of the pieces of critical evidence for the prosecution was that in Rob Hall's truck he had been carrying around these printed-out emails between him and his wife, and these emails were talking about the affair with Emmett, and so the prosecutor said 'He's angry. He went there angry,'" said Grey.

And then there's the matter of Rob's gun, which ironically was a gift from Kandi.

"The most damning evidence appeared to be the fact that Rob Hall's gun holster was in his center console, and a gun expert that testified said you don't take your gun out of your holster unless you intend to aim it at somebody or something," said Grey.

But what exactly happened during those critical 17 minutes before the shooting is actually a mystery, leaving attorneys to fill in the blanks.

"So there are these wedges of surveillance tape that are missing, that don't show Rob getting out of his car, so we don't know. Did he jump out of his car with his gun pulled? We don't know. Did he casually get out of his car and walk over? We can't see anything," said Grey.

And neither did anyone else. There was only a single witness to the fatal shooting: Kandi Hall.

"You also have just kind of this incredible eyewitness who didn't actually eyewitness anything, she says," said Grey.

"She says" being the key point here. In fact a lot of what Kandi said on the stand changed depending on the day.

One of many stories she changed was whether or not Rob and Emmett actually had physical contact in the moments before the shooting.

"She would tell them what they wanted to hear basically," said Grey.

Even the judge was at his wits' end.

"Frankly, any testimony by Ms. Hall, in my 31 years on the bench, I don't think I've seen a witness more thoroughly discredited in the course of a proceeding," Judge Michael McLaughlin said in an audio recording from court.

And to add insult to injury, Ashlee, Emmett's wife, was shocked by how lovey-dovey the Halls carried on in court. The two rekindled their failing love after the shooting.

"Her and her husband at the trial were very loving to each other, saying 'I'm sorry, I still love you,'" said Ashlee.

Then after both sides rested, the moment Ashlee had been waiting for.

"I remember the last day walking in as the judge was standing up to announce the verdict, and I thought I was gonna have that 'Beauty and the Beast' rooftop, the light shines through you and everything feels whole, and instead the judge stood up and announced everything, and all I could see was these two mothers," said Ashlee. "A mother whose son was now gonna be in jail for a long time, and a mother whose son had been killed, and it like, it tore me apart realizing that there's other people hurting probably just as much as me."

The jury reached a unanimous verdict: Robert Dean Hall was found guilty of second-degree murder.

Robert Hall was sentenced to 30 years in prison. He'll be eligible for parole in 2030, just past his 60th birthday.

And as for Kandi Hall, she was sent to prison -- but not for that fatal night. She served 18 months for embezzling from another law firm.

But for Ashlee's story, her next chapter is one of incredible strength and courage. The mother is five is now a motivational speaker and has written three books.

What do you tell your kids about their father?

"They'd come home from school, 'Hey, my friend said he saw on the news this and this and this.' And at first I was tempted to lie. 'He got in a wreck, everything's going to be OK.' And then I realized that lies are what got us where we were. So now we talk about his good qualities, but we also talk about the choices that he made, and how our choices do determine our destiny. And I think for them, it's given them a reason to try harder in life and to make good choices, and to always put your best foot forward."