MIAMI (CBSMiami) — Michael Hernandez, who was convicted of killing his middle school classmate when both were just 14 years old, has died in prison, according to the Florida Department of Corrections.

Hernandez was 31-years old.

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Authorities have not yet released the manner of death but our source tells us he collapsed in prison and it was caught on video.

Hernandez had been sentenced to life behind bars for the February 2004 stabbing death of Jaime Gough at Southwood Middle School.

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Hernandez got a second sentencing hearing in 2016 because of a U.S. Supreme Court ruling that juveniles could not get mandatory life sentences. In February of 2016 he said to the court “It hurts me how senseless it was because he was always such a good friend to me and I wanted to apologize to his family and his mother.”

But prosecutors did not buy his apology, after hearing chilling recordings of jail calls from Hernandez joking about his inability to cry, saying he’ll have to stab himself to make it happen in court.

Testimony also showed that Hernandez remained obsessed with violent imagery and music that glorified death and murder. Officials said Hernandez wanted to become a serial killer and had a list of victims. His prosecutor Gail Levine let Hernandez have it in court saying, “Because as you sit here today you cry on cue. That’s what you do. What was stupid is that you didn’t think I was smart enough to listen to your calls.”

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(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)

CBSMiami.com Team