A MARTÍNEZ, HOST:
In a few short years, Aaron Hernandez moved from NFL star to murder suspect. He was convicted of killing one person before being cleared of two other murders. In prison, Hernandez killed himself, and after his death, the former New England Patriots tight end was diagnosed with brain disease. And we want to note for listeners, this report includes several references to suicide. Member station WBUR and The Boston Globe have now obtained Hernandez's final phone calls from prison. As Todd Wallack reports, the calls add to questions around his death.
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UNIDENTIFIED ANNOUNCER: And that's Aaron Hernandez, a rookie tight end, inside the...
TODD WALLACK, BYLINE: Aaron Hernandez quickly became a star after he was drafted by the New England Patriots, playing alongside future Hall of Famers like Tom Brady. He was considered one of the best tight ends in the league and made a Super Bowl appearance against the Giants in 2012. His career ended abruptly a year later when Hernandez was arrested and accused of killing three people. But in April 2017, he was acquitted of a double murder in Boston. And in his last phone calls from prison, Hernandez sounds jubilant.
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AARON HERNANDEZ: Another beautiful day, man - beautiful day, man. It's just like the whole world just came off my back.
WALLACK: Hernandez remained behind bars for another homicide, killing his friend Odin Lloyd. But he was appealing the case and seemed optimistic.
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HERNANDEZ: Thing work out perfect, man. I'm going to fight to the end to get myself home. When I touch down, it's game time, you know?
WALLACK: But just days after the acquittal, Hernandez killed himself. His attorney, George Leontire, struggled to understand why.
GEORGE LEONTIRE: It didn't make sense. I can only tell you we were shocked. I think everyone involved was shocked.
WALLACK: It's not unusual for someone to seem hopeful before a suicide, says Eileen Davis. She runs Call2Talk, a suicide prevention hotline.
EILEEN DAVIS: Oftentimes individuals that do take their own lives do sound more upbeat and positive in the hours, days, weeks prior to the actual suicide or suicide attempt.
WALLACK: She says that can make it hard to predict these deaths. Plus, suicide is complicated with lots of factors. In the case of Hernandez, one potential factor is that he had a brain disease called chronic traumatic encephalopathy, or CTE. It's been linked to head injuries and contact sports like football. CTE can cause people to be aggressive or even violent. And researchers have seen many cases where people with CTE died by suicide.
ANN MCKEE: There's just a lot of impulsivity and very sudden changes in behavior.
WALLACK: That's Dr. Ann McKee, who leads Boston University's CTE Center. The disease can only be diagnosed after someone dies by examining samples of the brain under a microscope. McKee says Hernandez had one of the worst cases she'd ever seen in someone so young. He was just 27. Another possible factor is evidence that Hernandez smoked a synthetic drug called K2 in the days before his death. Nora Volkow is director of the National Institute on Drug Abuse. Volkow says K2 can have dangerous side effects, especially for people like Hernandez with brain injuries.
NORA VOLKOW: So it's a Russian roulette when people take these drugs because they do not know, first of all, what is the chemical they are consuming.
WALLACK: Eight hours after his last phone call, guards found Hernandez dead in his cell and religious writings on the walls in blood. The upbeat phone calls still leave many questions about his death, but the story is a stark reminder of the problems with illegal drugs in prisons across the country and the risk of CTE athletes still face on the field today.
For NPR News, I'm Todd Wallack in Boston.
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MARTÍNEZ: If you or someone you know is in crisis, call or text 988 to reach the Suicide and Crisis Lifeline. Transcript provided by NPR, Copyright NPR.