Video shows a man stomp on teen's bike after authorities said he knocked the boy off the bike and punched him in a frightening attack in Santa Clarita. The man, seen on video recorded by the teen, also slashed the boy's bike tires with a knife, the sheriff's department said. Lalania Bidwell, the teen's mother, said the friend swerved to avoid the man, whose bike had no reflective equipment. The teen eventually got away from the man and began recording video of him stomping on his bike. The teen can be seen in the video waving his hands as he desperately called to drivers for help.