A swarm of high-powered bikes had almost taken over all three lanes of a New York street.
Caught between them was a 33-year-old Range Rover driver, his wife and their two-year-old daughter.
When one of the motorcycles apparently slowed to a near-stop in the centre lane, it was struck by the vehicle and its rider was knocked to the ground.
The SUV and its occupants stayed put at first. But moments later, surrounded by the fallen biker's fellow riders, it sped through the crowd and set off a chase, The New York Times reported.
The chase ended in violence after the SUV got stuck in traffic.
Several pursuing motorcyclists pulled the driver from the vehicle and beat him, police said.
The six-minute video of the incident, which happened on Sunday, has since gone viral.
New York police commissioner, Raymond W Kelly, said the motorcyclists had been part of a planned but unauthorised event in which hundreds of riders gathered outside of Manhattan and intended to descend en masse into Times Square.
The New York Post identified the SUV driver as Mr Alexian Lien and his wife as Ms Rosalyn Ng.
Police revealed the bikers started to damage the vehicle after Mr Lien hit a motorcyclist.
Fearing for the safety of his family, he sped off, hitting several other bikers on the way.
The family was eventually brought to a standstill in Manhattan traffic and immediately, bikers began to attack the vehicle.
One biker removed his helmet and threw it against the driver's window, smashing it; the second tries to punch through the rear door window, where the child was seated.
Then the footage stops. The video has already received many comments, most of them in support of Mr Lien.
Netizen Sgt Pepper said: "I would do exactly the same thing. They're intimidating him and he's probably fearing for his life."
Another, known as "zacarra", said the driver acted in "self defence".
"Did you see the biker break (sic) check him in the beginning. This poor guy was running for his life from the start," zacarra wrote.
Police said the collision appeared to have been inadvertent on the part of the driver.
At least one rider present, Mr Rene Towles, 43, had a different story to tell.
Mr Towles, who belongs to a Brooklyn motorcycle club, told The New York Times: "No biker became aggressive with the driver after the incident.
"People were just trying to find out what just happened."
A New York Police Department spokesman told MailOnline that Mr Lien was taken to hospital and treated for cuts to his face and body.
He said there were no other injuries reported from the incident.
No one has been arrested and police are still investigating and examining the evidence.
Get The New Paper for more stories.