Sources: Southwood Middle School Killer Michael Hernandez Died Of Possible Drug Overdose

MIAMI (CBSMiami) – The current theory on Michael Hernandez's death inside the Columbia Correctional Institution is that the 31-year-old died from a possible drug overdose, according to two sources familiar with the matter.

There were no signs he had been attacked by any other inmates and the prison has video of him collapsing to the ground.

He was formally declared dead at a medical center in Lake City near the prison. An autopsy will be performed and the FDLE will investigate.

Drugs have long been a problem within prisons, but the newest threats are K2, a synthetic cannabinoid, and Suboxone, which is used to treat opioid addiction. Both drugs are sneaking their way into prison on the backs of stamps on letters sent to inmates.

Inmates receiving those letters can either get high licking the stamps or selling it to other inmates. Suboxone is particularly dangerous, according to medical experts, because it is both addictive and can slow or stop a person's breathing.

Hernandez was serving a life sentence for the murder of his middle school classmate Jaime Gough in 2004.

Hernandez, who fantasized about being a serial killer, lured Gough into the school bathroom and stabbed him more than 40 times.

The Miami-Dade State Attorney's Office released the following statement on Hernandez's death:

"Jaime Gough's brutal murder ended a promising young life and forever scarred his family. For them, this news still must tear at their hearts. I have always felt that Michael Hernandez' family were also Michael's victims. Upon his conviction, Michael Hernandez' family was also scarred by Michael's actions. My sympathies to both families."

On Sunday, CBS4 spoke to Gough's parents about the death of their son's killer.

"I don't feel joy, just sad," said Maria Gough.

Jorge Gough said learning of the death, "It was shocking and not expected at all."

The couple said their thoughts were with Hernandez's parents.

"I know how painful it is to lose a child," said Maria Gough.

The Goughs say they forgave Hernandez long ago.

"You have a choice to make. You can choose more hate and anger, and it would not be peaceful," said Jorge Gough.