An off-duty undercover cop who was riding with a large gang of motorcyclists in New York last month, not only witnessed other riders dragging a man out of his SUV and brutally assaulting him in front of his wife and child, the cop allegedly participated in the attack.

Originally, the seven-year veteran narcotics officer claimed he didn't do anything while members of the ride along punched, kicked and slashed at the victim's face because he arrived at the scene when the attack was ending. But according to new video evidence obtained by the New York Post (from the paper's "disgusted" sources), the unidentified undercover officer can be seen punching one of the SUV windows while the attack is still ongoing. (Update, 5:53 p.m. CBS News reports the undercover officer in question has been arrested for his part in the assault.)

In total, six officers were allegedly part of the group of motorcycle riders when the attack went down. It's unclear so far why they were riding with the group that NYPD was already on alert for, or why any of them failed intervene when things got ugly. The unidentified undercover officer originally got himself in trouble for not reporting his presence at the scene of the crime until more than three days after the attack. He has since turned in his badge and gun and has been reassigned pending an internal investigation. 

On September 29, Alexian Lien, 33, was driving in a Range Rover on New York's West Side Highway with his wife and two-year-old daughter when a group of motorcycle riders pulled in front of him. An accidental bump occurred, and the gang started to surround Lien's SUV. When the father sped away because he was threatened, scared and outnumbered, he ran over a few of the riders, paralyzing 32-year-old Edwin Mieses, who has since teamed up with power lawyer Gloria Allred. The bike gang raced after the SUV and pursued Lien into New York City traffic where, finally having him cornered, members of the group proceeded to smash the driver side window and drag Lien out of the car. Lien was assaulted and hospitalized following the attack. Everything leading up to the attack was caught on video:

At least four bikers have so far been been arrested for their roles in the attack. Twenty-nine-year-old Craig Wright, 37-year-old Reginald Chance, and 35-year-old Robert Sims were all arraigned on assault charges. Prosecutors decided not to formally charge the fourth, 43-year-old Allen Edwards, for his role in the attack. To make things even stranger, the man who organized the ride, Jamie Lao, who goes by the name Hollywood Stuntz online, told the website Global Grind he tried to cancel the event at the last minute "due to overwhelming pressure from the police."