A father and his 10-year-old son were killed when a fire truck responding to a blaze crashed into their vehicle in California.

A CAL FIRE engine was heading to a fire in the San Bernardino National Forest east of Highway 74 on Friday, June 5, when the collision occurred, the fire department said, according to NBC affiliate KNBC.

The California Highway Patrol (CHP) said that the fire truck, which was traveling northbound on State Street with its emergency lights and sirens activated, struck the Mini Cooper sedan moving west on Gibbel Road in Hemet, the Los Angeles Times reported.

Authorities said there were three people inside the Mini Cooper and all wore seatbelts, according to CW affiliate KTLA. The Mini Cooper driver, a 43-year-old male from San Jacinto, was pronounced dead, and a 10-year-old boy who was in the front passenger seat was taken to a hospital and succumbed to his injuries.

The CHP added that a third passenger, another boy, sustained minor injuries. The identities of the two fatalities are unknown, but Fox affiliate KTTV reported they were father and son.

Meanwhile, three people from the fire engine, among them the driver and two firefighters, were taken to Inland Valley Hospital for medical evaluation. They were later released, KTTV reported.

Alcohol or drugs are not suspected to be factors in the crash, said the CHP, and the investigation is ongoing.