A man visiting a campground in San Diego was killed Thursday when his Smart car rolled over him as he tried to unhitch the vehicle from a motorhome, officials said.

California Highway Patrol Officer Jeff Christy said the man – a 71-year-old from Federal Way, Washington, now identifed as James R. Colie – had just returned to the U.S. from a trip to Mexico and was staying at a campground on Potrero Park Drive in Potrero, an area in southeastern San Diego.

Colie had been driving a motorhome and towing a Smart car.

Christy told NBC 7 the car was attached to the rear of the motorhome with an aftermarket part that attached to the front bumper of the car. This allowed the car to be towed on all four wheels, Christy said.

After parking the motorhome at the campground, Christy said the man began to uncouple the hitch between the rear of the motorhome and the Smart car.

However, he had forgotten to set the emergency brake on the car.

When the hitch was released, the car began to roll. Christy said Colie ran to the car and tried to stop it from moving, but “was overcome by its momentum.”

The car rolled up and over Colie, pinning him underneath. Christy said Good Samaritans ran over and tried to lift the vehicle off the man, but just couldn’t do it.

CHP officials and firefighters were called to the campground and were able to lift the car off the man using jacks. However, Colie was critically hurt and died a short time later, Christy confirmed.

No one else was hurt in the incident.

The San Diego County Medical Examiner’s Office later said Colie had been camping with his girlfriend at the time of the tragic incident.

Christy said alcohol or drug impairment is not suspected in this case.