SACRAMENTO, Calif. (AP) — Former Nebraska star running back Lawrence Phillips has been found dead in his California prison cell and officials say they suspect suicide.

Guards at Kern Valley State Prison found the 40-year old unresponsive in his cell.

He had been housed alone in a segregation cell since April 2015 after he was suspected of killing his cellmate.

Phillips was a former No. 1 draft pick of the before his NFL career was cut short by disciplinary problems.

Phillips went to prison in 2008 to serve a sentence of more than 31 years after he was convicted of twice choking his girlfriend in 2005 and of driving his car into three teens later that year.