ALAMEDA COUNTY, Calif. (KRON) — The in-custody death of an inmate at Santa Rita Jail is being investigated by the Alameda County Sheriff’s Office, according to a press release from Alameda County. Charles Johnson, 45, suffered a medical emergency at the jail and was transported to Stanford Health Care — ValleyCare Medical Center in Pleasanton.

Johnson had been booked into the jail on Jan. 27 by the Oakland Police Department for violating a served protective order. Johnson was screened and cleared for incarceration by custodial medical and mental health staff during his intake, the press release states.

Several days later, on Feb. 2, Johnson was found unresponsive in his assigned cell during the distribution of medication in his housing unit. He was the sole occupant of the cell at the time. Deputies requested emergency medical services and assisted medical staff in administering life-saving measures until paramedics arrived. He was subsequently taken to the hospital and placed on a ventilator.

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While on a ventilator, Johnson’s condition failed to improve and he was subsequently taken off the ventilator and declared deceased by a hospital physician on Saturday, Feb. 4. A preliminary investigation revealed no signs of obvious trauma or foul play, according to the county. Authorities also say there were no medical or mental health red flags identified during Johnson’s intake.

His next of kin were notified and they were able to spend time at the hospital with him before his death. An investigation is ongoing. Johnson’s cause of death will be determined by the Alameda County Medical Examiner.