LA SALLE, Colo. -- Authorities in Weld County have a real mystery on their hands.

They know how a wandering caribou died Tuesday, they just don't know where it came from.

Gene Fisher, a Colorado Department of Transportation worker, says he spotted the large animal grazing along a highway near U.S. 85 Tuesday just south of the city of La Salle. A train whistle spooked the animal and it jumped into the path of a passing car and died on impact.

The caribou buck had a large rack of antlers. Colorado State Trooper Shannon Straley said he counted 45 points on the antlers. The animal weighed about 350 pounds.

A Colorado Department of Transportation employee witnessed the accident and called the state patrol to report it.

"I got the call, and the dispatcher said a car hit a caribou, and I said, 'A what?'" said Straley.

Caribou normally live in the arctic regions of northern Canada, Alaska and Greenland.

"We don't know where a caribou would come from," state Division of Wildlife manager Chad Morgan told the Greeley Tribune in Wednesday's editions. "We don't know of any farms that have them in this area. I've been here four years, and I've never seen one."

The Colorado Department of Agriculture, Division of Wildlife and State Veterinarian's office said they had no records of caribou in Colorado.

La Salle is located in Weld County, about 45 miles north of Denver.