9-1-1 crew member Rico Priem, whose May death brought fresh concern over working hours on sets, died of sudden cardiac dysfunction, according to local officials in Los Angeles. His body was found inside his crashed vehicle after he’d worked two consecutive 14-hour overnight shifts.

Priem, a grip for the Fox procedural, died on May 11 of sudden cardiac dysfunction and cardiomegaly with left ventricular hypertrophy, according to records from the Los Angeles County Medical Examiner’s Office, which released his autopsy results this week. Priem’s cause of death was deemed to have been natural, the office said and there was no detection of alcohol or drugs in his system at the time of his death.

The autopsy results negate the suggestion by his union that his death was a result of drowsiness after overwork on the show’s set that led Priem to drift from the highway and die when the vehicle crashed last month. After the news and circumstances of Priem’s death broke, his union released statements that suggest unsafe working hours led to the 66-year-old’s death. 

“We are fully committed to the safety and the well-being of all our members and express our heartfelt condolences to the member’s family,” IATSE said in a statement. “Workers have a reasonable expectation that they can get to work and come home safely. No one should be put in unsafe circumstances while trying to earn a living.”

An IATSE union leader previously confirmed with The Hollywood Reporter that Priem was a day player on 9-1-1 and his shift on Friday was his second 14-hour production day in a row. He’d left work a little after 4 a.m. on Saturday morning.

According to the California Highway Patrol, Priem’s Toyota Highlander was found overturned and obstructing the right lanes on the 57 freeway in San Dimas; the crash was reported around 4:27 a.m. on Saturday. According to CHP, Priem’s vehicle drifted off the road and up an embankment before flipping onto its roof. Priem was found dead at the scene.

In a statement following the news of Priem’s death, 20th Television said, “On behalf of the studio and everyone at 9-1-1, we send our sincere and deepest condolences to Rico Priem’s family and friends.”

IATSE is prioritizing imposing financial penalties for long work days and missed rest periods during its ongoing negotiations with studios and streamers after several accidents have been seen on sets this year. In February, J.C. “Spike” Osorio died after falling from the rafters at Radford Studios while he was working as a rigger for Marvel’s Wonder Man. In April, multiple crew members were injured in an action sequence that did not go as planned on the set of Amazon-MGM Studios’ The Pickup. OSHA investigations for both incidents remain ongoing.