According to USA Today, former Nebraska running back Lawrence Phillips died at the age of 40.

He was reportedly found dead on Wednesday morning at Kern Valley State Prison, California Department of Corrections and Rehabilitation spokeswoman Terry Thornton told USA Today. The death is being investigated as a possible suicide.

Phillips was facing murder charges and possibly the death penalty after the alleged murder of his cellmate, Damion Soward. He was in prison because of a seven-year term for felony assault with a deadly weapon and he had an additional 25-year sentence for domestic violence on his girlfriend.

A key cog on Nebraska’s back-to-back national championship teams in the mid-1990s, Phillips created a controversy when he started in the 1995 Fiesta Bowl after he was suspended for assaulting his girlfriend at the time.

He was drafted No. 6 overall by the St. Louis Rams but legal troubles ended his NFL career after just four seasons.

Former Nebraska coach Tom Osborne told the Associated Press that Phillips’ death caught him off-guard.