COPPER CANYON, Texas -- Authorities in the Denton County town of Copper Canyon said they are looking for a motorcyclist who has been terrorizing horseback riders on a local trail.

In one case, a rider was thrown from her horse after the cyclist appeared to intentionally try to frighten the animal. People who ride the trails said they are concerned and hope that the person is arrested soon.

"Somebody could be badly hurt -- not to mention the horse -- and there's all kinds of opportunity for that to be just a disaster," said Deb Valencia, a trail rider.

The Denton County constable's office is looking for the biker, and the mayor in Copper Canyon wrote an editorial in the paper asking for the public's help.

The trails are owned by the Army Corps of Engineers, and motorcycles are illegal on them.

Several people have reported seeing the motorcycle, which is described as dark blue or purple with some yellow on it. Witnesses said the rider wears a full motorcycle suit with a face mask on the helmet that has made it harder for people to get a good description.