Authorities are investigating after a man was found critically injured on a trail at Antelope Island State Park and later died.

Two women came upon the 55-year-old trail runner — identified as Larry M. Adams of Syracuse — on the Lakeside trail, according to a news release. A medical helicopter transported the man to a local hospital.

Officials don’t know what happened to the man — there were no known witnesses — but said his injuries are consistent with a bison attack.

A herd of hundreds lives in the state park, which is connected to the Great Salt Lake’s southeastern shore by a 7-mile-long causeway. Mule deer and pronghorn also live at the park.

The bison have been known to charge people who get too close. It happened a few times last year on the Lakeside trail.

Park officials urge visitors who encounter bison to back away and return to where they came from, or leave the trail to give the animal a wide berth before passing.