A person riding a horse on a highway in eastern Idaho has died after the rider and horse were struck by a semi.

The Idaho State Police Department said the crash occurred at 8:23 p.m. Monday, September 18 along Old Butte Highway north of Hamer, Idaho, which is in Jefferson County north of Idaho Falls.

A 59-year-old male was driving a 1998 Peterbilt semi northbound when he struck the 56-year-old male riding the horse in the northbound lanes. According to ISP, the semi struck the rear end of the horse. The rider of the horse was thrown and succumbed to his injuries. The horse also succumbed to its injuries.

The incident remains under investigation by the Idaho State Police.