Seattle police are investigating how a recreational vehicle pinned and killed a 73-year-old man Thursday in the driveway of a South Beacon Hill home.

The incident occurred about 2:30 p.m. when the man and his adult son were trying to move a trailer up the driveway of a home in the 8000 block of 36th Avenue South, said Seattle police spokesperson Sgt. Randy Huserik.

The son attempted to back his truck and fifth wheel trailer from the street up the incline of the driveway, Huserik said.

“As he was reversing, he realized he had struck his fence,” a post on the department’s website added. “However, unbeknownst to the driver, a family member had been pinned between the fence and the trailer and was severely injured.”

Seattle Fire Department medics arrived and tried to save the man, but he died at the scene.

An officer trained as a drug recognition expert responded to evaluate the driver and detected no signs of impairment, the Police Department reported. Traffic collision detectives who responded to the scene were still investigating Thursday night.