An autopsy has determined that former NFL star Lawrence Phillips committed suicide by hanging himself with a bed sheet in his prison cell.

USA Today reports the former pro athlete was found unresponsive on Jan. 13 at Kern Valley State Prison with a note taped to his chest that read, “Do Not Resuscitate.”

Phillips, who was serving a 24-year sentence for other offenses when he was pronounced dead, was scheduled to begin trial on murder charges in the death of a cell mate.

A toxicology report found no illegal drugs or psychiatric medication in Phillips’ system at the time of his death.  The final coroner’s report states Phillips died of asphyxia due to hanging. It revealed that a bed sheet had been ripped in half, knotted and tied around Phillips’ neck. He was found hanging from a five-foot high, metal television shelf.

The forensic pathologist who conducted the coroner’s report also found a photo of Phillips and an unidentified child along with a note in his left sock. No details were provided about the note. The note on Phillips’ chest read, “Do not Resuscitate” and was written on a small piece of paper torn in half. Phillips was being housed in a segregation unit at the time of his death because he was a suspect in the death of another inmate. Prison officers were directed to check on him twice an hour every 35 minutes. He was last seen alive around 11:35 p.m. Jan. 12.