An inmate was pronounced dead while in custody Tuesday morning at the Martinez Detention Facility, according to the Contra Costa County Sheriff's Office.
Just before 7:45 a.m., a deputy found the man hanging in a shower.
He was unresponsive, and life-saving efforts by medical staff and firefighters responding to the jail were unsuccessful.
His name is being withheld pending notification of his next of kin.
The death is under investigation by the sheriff's office and the county's district attorney.