The death of a Berrien County Jail inmate in February was ruled a suicide.

A forensic investigator determined that 24-year-old Martell Hadley died of asphyxiation after an officer found him hanging in his cell the night of Feb. 27, according to the Berrien County Prosecutor’s Office.

He used a bed sheet tied to a cold air vent, the prosecutor’s office said.

Recordings from his telephone calls to other people revealed that Hadley was feeling frustrated and depressed about a personal issue. He wrote a letter about that issue while in his cell the night of Feb. 27, but police are not calling the letter a suicide note.

Hadley’s family arranged for a private contracted autopsy, but the results of that has not yet been released.