A man and his horse died after being hit by a car Monday evening in Riverton.

The man, 35, was riding his horse about 7 p.m. near 2200 West and 13800 South when a westbound driver hit them, said Unified Police Sgt. Melody Gray. The man died at the scene; the horse was euthanized, Gray said.

The driver stayed at the scene and is speaking with investigators, but detectives don’t yet have a “definitive answer” for why the car struck the horse and rider, Gray said.

“It’s possible the sun was in his eyes,” Gray said. She said it was not yet clear where the horse and rider were when they were hit — on the shoulder or in the roadway.

Police were not releasing the victim’s name late Monday.