'He broke her heart … that's exactly where she was aiming': Texas family, PI believe jealous girlfriend shot son Jonathan Crews was found shot in his bed and his death was ruled "undetermined."

 -- Frustrated by local law enforcement’s handling of their son’s mysterious death, a Texas family enlisted the help of a former stay-at-home mom turned private investigator to examine the case and filed a wrongful death lawsuit against the woman they allege shot him.

Jonathan Crews, a 27-year-old urgent care center director from Coppell, Texas, was found dead from a gunshot wound while lying in his bed. His girlfriend at the scene said he committed suicide, but his family filed a lawsuit alleging that his girlfriend shot and killed him in a jealous rage.

“I knew it didn’t make sense,” said his mother, Pam Crews. “He didn’t do this. I know he didn’t do it.”

On Feb. 2, 2014, Super Bowl Sunday, long after the game was over, Crews’ girlfriend, 26-year-old Brenda Lazaro, a kung fu instructor, called 911 and told the operator that Crews had shot himself in bed. According to the police report, Lazaro told detectives she had arrived at Crews’ apartment earlier that afternoon and she and Crews had fought about another woman. Lazaro claims they then ate, watched TV, and talked while she sat on the floor and Crews lay in bed.

“We were just having a discussion and we were just talking,” she explained earlier to the 911 operator. “He just said that he loved me and I didn't need to leave him and ... he said that he was going to prove that he loved me.”

That’s when Lazaro said Crews told her to cover her ears. Then she said she suddenly heard a gunshot and when she stood up, she realized Crews had apparently shot himself in the chest.

But Crews’ family said they soon felt like something was off about Lazaro’s story. She stayed with the family immediately after his death but didn’t show up to Crews’ viewing or his funeral. Then hours after the funeral, Crews’ sister, Danielle Crews, who had been friends with Lazaro for years, said she went “crazy.”

“She was complaining she wasn’t involved enough,” Danielle Crews told “20/20.” “She kind of wanted the funeral to be about her and their love, and I thought, ‘that’s really selfish.’”

Crews said Lazaro sent her a stream of bizarre messages, saying in part that, “None of you thought for a second to acknowledge our love during his funeral.”

“I was just mad,” Danielle Crews said. “My brother just died, I just went to his funeral, like, how dare you say these crazy things? How dare you make demands.”

Soon the Crews family hears from couple Emily and Jacob Ramsey, Jonathan’s closest friends. Emily Ramsey told “20/20” they went out on a double date with Crews and Lazaro a few months before his death, and that Lazaro apparently became jealous when Emily and Crews gave each other a hug to say hello.

Danielle Crews said two months after her brother’s double date with Emily and Jacob Ramsey, she received texts from Jonathan saying Lazaro was fighting with him over his friendship with Emily. He texted his sister that his choices were “A) Fight it and try to make it better. B) Choose Brenda C) Refuse to give up either and see if Brenda ends it. D) End it with Brenda now.”

"Later that same day, he told me ‘D’ was his final choice,” Danielle Crews said.

On Feb. 2, 2014, the following day, Emily Ramsey said she, Crews and Jacob Ramsey met for lunch and as Crews was telling her that Lazaro felt threatened by their friendship, Emily said Lazaro called his phone.

“Jonathan looked at me and said, ‘She wants to talk to you,’” Emily Ramsey told “20/20.” “She just started yelling at me and telling me that I was a disrespectful little girl. ...'You hug my man, that’s so rude.'”

That night, Emily said she got a weird text from Crews’ phone that said, “I want to die.”

“I was just kind of like, ‘What’s going on?’ Like, that’s so weird,” Emily Ramsey said. “And I texted him back, saying like, ‘Hey love, are you OK? What’s going on?’”

Emily said she and Jacob tried to call Crews multiple times but the calls went unanswered. The next day, Jacob Ramsey said Crews’ brother Christian called him.

“He just said it -- ‘Jonathan’s dead,’” Jacob Ramsey said. “I just kind of immediately broke down.”

Once Emily heard what had happened, she said she immediately thought it had been Lazaro who had texted her from Crews’ phone. She called the police and told Crews’ mother.

“My mother’s heart was like, ‘OK, this makes sense now,’” Pam Crews said. “I knew right then ... that she [Lazaro] had done it.”

The medical examiner ruled Jonathan Crews’ death as “undetermined.” According to local police, there wasn’t enough evidence to arrest anyone.

Unsatisfied and craving justice for their son, the Crews family enlisted the help of private investigator Shelia Wysocki. She had been a stay-at-home mom until she helped crack open the case of her college roommate’s murder two decades earlier. Now she helps other families with mysterious death cases.

Wysocki has spent 18 months investigating Jonathan Crews’ death and she told “20/20” she believes there are numerous red flags that point away from a suicide.

One red flag, Wysocki argues, is that gunpowder was found on top of his right hand, but none on his right palm and his left hand had no gunpowder residue on it.

“If you’re going to kill yourself, generally you shoot in the mouth, you shoot upward,” she said. “You don’t lay down, getting ready for bed and shoot yourself.”

She also believes that the bullet trajectory for how he could have shot himself in the chest is off. Crews was right-handed but was shot on the left side of his chest. The bullet passed through his body and lodged in the mattress. Wysocki believes for Crews to have shot himself, he would have to have the gun pointed downward.

“What’s interesting is in the 911 call, Brenda says he was shot in the heart,” Wysocki said. “I believe that’s exactly where she was aiming. He broke her heart that night by breaking up with her.”

But Dr. Jonathan Arden, a forensic pathologist with 20 years experience as a government medical examiner, cautions against making any conclusions about the gunpowder findings.

"The forensic science laboratory did extensive gunshot residue testing for the shooting of Mr. Crews, and they found, or they detected gunshot residues on the hands of the girlfriend and on one of his own hands," Arden said. "Now unfortunately, gunshot residues are rarely definitive or decisive in terms of uh, determining if a gunshot was self-inflicted or not, or even for that matter who held the gun or shot the gun."

Crews’ family filed a wrongful death suit against Lazaro in January 2016, in order to force her to have to testify under oath but during her deposition, she invoked her Fifth Amendment right not to incriminate herself.

“I thought that was awful,” said Pam Crews of Brenda’s deposition. “If she can't answer a single question, particularly the question about, "Did you kill him." If you can't say no to that, it warrants a lot further investigation”

Sheila Wysocki tracked down Lazaro’s ex-boyfriend Matt Kirk, who said Lazaro “almost ruined my life,” during his sworn deposition.

“She was jealous of any woman I talked to,” Kirk testified. “She would always say things such as, ‘You like her?’ … She just got crazy whenever I went around any girl.”

Kirk said Lazaro harmed herself regularly, more than 100 times, and said the worst time was when he went to visit his newborn niece in the hospital.

“She didn’t want me around my sister-in-law,” Kirk testified. “It was that bad. She was cutting herself in my bathroom… ... she was crying and her hand was full of blood.”

In a statement to ABC News, Coppell police said they do not “have enough evidence to present to a grand jury” to charge anyone in Crews’ death and they have classified the investigation as “inactive,” but not closed meaning there currently are no more leads to pursue.

Lazaro, who is now married with a baby, declined ABC News’ requests for comment. In court documents, she denies all the allegations against her.

The civil wrongful death trial is set to begin in September 2017.

Trying to move on, Pam Crews carries some of the ashes of her son in a necklace she wears every day, still searching for answers.

“This will never be all right because he’ll never be back, but the right thing needs to happen,” she said. “In the end, we’ll know that we spoke for Jonathan to the best of our ability, and he would have done that for us.”