BEAVERTON - A robbery near the Beaverton Transit Center was averted earlier this week due to what police said were the combined efforts of officers, victims and a passing bicyclist.

Police arrested Jentre J. Hoffman, 23, Tuesday after he allegedly tried to rob Alex Negreanu, 17, of Portland.

At about 10:25 p.m., TriMet police were patrolling the Transit Center, 4050 S.W. Lombard Ave., and were approached by a man who said he kept hearing a woman screaming for help near the pedestrian bridge.

Officers ran toward the bridge and heard Ashley Birkhead, 16, of Hillsboro, screaming "Help! Call 9-1-1!" said Detective Pam Yazzolino, spokeswoman for the Beaverton Police Department.

Yazzolino said officer crossed the bridge, near the Canyon Place Shopping Center, and found the girl standing near two men, who were fighting. Yazzolino said that Birkhead and Negreanu had crossed the bridge and were heading south in the mall when Hoffman approached and grabbed Negreanu's hat from his head. When the teenager asked for it back, Hoffman punched him the face, according to Yazzolino.

Hoffman then grabbed other things from Birkhead and Negreanu and said he was taking them, too, she said. When police arrived, she said, Hoffman ran off.

A passing bicyclist, Dorsett Peake, 39, of Portland, heard police call for Hoffman to stop and chased the fleeing man to the MAX tracks, Yazzolino said. Peak knocked Hoffman down, giving police enough time to catch up and make the arrest.

Hoffman was held in the Washington County Jail in lieu of $20,000 bail on accusations of third-degree robbery.

-- John Snell;

johnsnell@news.oregonian.com