Edgar Gearhart was 19 years old when he stabbed his mother and killed her boyfriend in a brutal stabbing in Sunbury in 2015.
Police say the violence erupted after a night of drinking and an argument over who was getting a ride home.
Neighbors at the time described a bloody scene.
"I walked down here, and there was blood all over the porch," said one neighbor.
Gearhart pleaded no contest to third-degree murder charges in 2016 and was sentenced to between 10 and 20 years behind bars.
But the young man served less than five of those years.
Officials at SCI Dallas in Luzerne County say the inmate was found unresponsive in his cell Thursday night.
Efforts to revive him were unsuccessful.
Edgar Gearhart was just 24-years-old when he died.
He spent about 20% of his short life in state prison.