OTAY MESA, CA – Investigators from the county Medical Examiner's Office and the Sheriff's Department are looking into the apparent stabbing death of a 41-year-old inmate at Donovan prison Thursday.

The inmate was not identified by authorities on Friday afternoon because they had not notified his relatives.

The prisoner was apparently stabbed about 5:15 p.m., said Lt. Dennis Brugos from the Sheriff's Department. The inmate had been walking through the prison yard with a group of 58 other inmates. They had just finished dinner and were heading to their cells, Brugos said.

An officer in a tower overlooking the yard said he initially noticed the inmate walking away from the rest of the inmates. Using his binoculars, the officer then noticed the prisoner was holding his neck and appeared to be in distress.

The wounded inmate was carried to a prison dispensary and treated, but at 6:10 p.m. he was pronounced dead, Brugos said.

An “improvised stabbing instrument,” made from a piece of metal, was later found near the area where the inmate first appeared to be suffering, Brugos said. Investigators believe it was the weapon used in the attack, he said.