At about 5 p.m., near 4100 South and West Temple, a man driving a sport utility vehicle saw a motorcycle he had helped customize, said Salt Lake County sheriff's Lt. Paul Jaroscak. The driver told police he ran the motorcyclist off the road and told him he was riding a stolen bike. A power line guide wire knocked the rider off the motorcycle, but he got up and forced his way into a maroon van with a woman and infant inside. He forced her to drive him to a house near 4500 South and 700 East, then let her go, Jaroscak said.

The woman returned to the scene of the accident and reported the incident to police, who returned to the house.

They did not find him, but know his name and are searching for him. A citation against the man driving the SUV doesn't look likely, Jaroscak said.

"He was doing what he thought was appropriate to stop the stolen motorcycle," Jaroscak said. "A citizen has almost as much right as the police to effect arrest."

Police do not believe the motorcyclist was injured, he said.

- Lindsay Whitehurst