YORK, S.C. - A Rock Hill man in custody on charges that he killed his mother and a neighbor died in jail from head injuries, authorities said Monday.

An autopsy found that 34-year-old Joshua Grose died from blunt force trauma to the head, York County Coroner Sabrina Gast said.

Grose was pronounced dead about 3 a.m. Sunday at a hospital after repeatedly hurting himself in jail. Sheriff’s spokesman Trent Faris has said that guards called paramedics after finding Grose unresponsive.

Guards earlier stopped Grose from drowning himself in his jail cell toilet and put him in a restraining chair after he repeatedly hit his head against the wall, Faris said.

When officers attempted to put a helmet on Grose, they noticed a cut on the back of his head. Paramedics were called but said the cut didn’t require stitches, so authorities chose not to transfer Grose to the hospital then. Because he was so combative, a full medical exam couldn’t be p erformed, Faris said.

Grose was in cardiac arrest when paramedics were called back about a half-hour later, authorities said.

Grose had been booked at about 11 p.m. Friday on charges of murder, attempted murder and grand larceny.

“From the moment he was booked into the jail, he was very combative and very uncooperative with our detention officers,” Faris said during a news conference with reporters on Sunday.

Deputies have said that Grose ran over 53-year-old Sandra Thomas while trying to steal her car, then beat up and ran over his mother, 65-year-old Sandra Grose. Both were found dead in their yards Friday. A 60-year-old man was taken to the hospital.

The State Law Enforcement Division is investigating Joshua Grose’s death.