KNOXVILLE, Tenn. (AP) — Two people were killed this weekend during a multivehicle crash involving an ambulance on an east Tennessee interstate, authorities said, with one of the victims a passerby trying to help following an initial collision.

Three other people were injured in the crash in the eastbound lanes of Interstate 40 that officers responded to Saturday about an hour before dawn, the Knoxville Police Department said in a news release.

The department said based on the investigation it appeared two vehicles were involved in a rear-end collision that caused one vehicle to roll over into the median. The passerby had stopped to assist the other vehicle that remained in a travel lane when a private ambulance struck that vehicle, police said. The driver of the vehicle and the passerby were pronounced dead at the scene.

There were no patients in the ambulance, whose driver and a passenger suffered minor injuries. The driver of the overturned vehicle, who was ejected from the car, was taken to a Knoxville hospital with severe injuries, the release said. No charges had been filed as of Saturday, but the crash remains under investigation.

Names of the crash victims weren’t immediately released.