Former NFL running back Lawrence Phillips was found dead in his prison cell early Wednesday morning in what prison officials are calling a suspected suicide.

Staff conducting security checks at Kern Valley State Prison found Phillips, 40, unresponsive shortly after midnight. He was transported to an outside hospital, where he was pronounced dead.

Philips went into Kern Valley in 2008 to serve a 31-year sentence after being convicted of choking hid girlfriend in 2005 and later that year of driving his car into three teens at a pickup football game.

He had been charged with strangling his cellmate, Damion Soward, and on Tuesday, a judge ruled there was enough evidence to move forward with the trial. Phillips could have faced the death penalty if convicted.