The family, driving up the West Side on a sunny afternoon, suddenly found themselves surrounded by motorcycles. In front of their sport utility vehicle, and behind, buzzing past on either side. A swarm of high-powered bikes had all but commandeered the three lanes of the northbound Henry Hudson Parkway on Sunday, and caught between them was the 33-year-old driver of a Range Rover, his wife and their 2-year-old daughter.
When one of the motorcycles apparently slowed to a near-stop in the center lane, it was struck by the vehicle and its rider knocked to the ground. The vehicle and its occupants stayed put at first. But moments later, surrounded by the fallen biker’s fellow riders, it barreled through the crowd, setting off a chase that would end in violence after the S.U.V. became stuck in traffic on a side street in Washington Heights, the police said.
Several of the pursuing motorcyclists pulled the driver from the vehicle and beat him, the police said. As detectives were working on Monday to piece together the events that led to the assault, a six-and-a-half-minute recording captured on the helmet camera of one of the riders and posted to video-sharing Web sites showed the harrowing chase and the beginning of the attack.