BROOMFIELD -- A landscape worker is being treated for serious injuries at Denver Health Medical Center after being run over by a lawnmower he was riding Monday morning.

The accident happened at the Camden Apartments in Broomfield, next to the Omni Interlocken golf course.

Rescue crews say the man was mowing on a steep hill, lost his balance and fell off the mower. It them turned back on him and ran him over, cutting off one of his arms.

This happened during the Denver Broncos Alumni Golf Tournament, which was taking place across the street.

"We were about to tee off and the helicopter landed on the tee box," said golfer Daniel Adler. "They put his arm in an ice box."

According to rescue crews, commercial mowers usually have a safety mechanism in place that automatically shuts off the mower if someone falls off.

"Obviously the machine did not shut off as it should have," said Wendy Forbes of North Metro Fire Rescue.

OSHA was called in to see if the safety mechanism was bypassed or if it failed.

The man is a contract worker employed by Navarro Landscaping of Las Vegas. Workers there say the owner was flying into Colorado Monday night.