A police officer involved in the brutal attack on a SUV driver was arrested yesterday. Detective Wojciech Braszczok, 32, a ten-year NYPD veteran whose undercover work included posing as a protestor during Occupy Wall Street, was charged with riot and criminal mischief for the September 29th incident.

The confrontation between SUV driver Alexian Lien and a large group of motorcyclists unfolded when the two parties were jockeying for position on the Henry Hudson Parkway on September 29. Lien struck one motorcyclist, Christopher Cruz, and then stopped. But when the motorcyclists surrounded him, Lien hit the gas and plowed over motorcyclist Edwin Mieses, who is apparently paralyzed.

The motorcyclists chased Lien and eventually started attacking his car at 178th Street—with his wife and baby daughter inside the vehicle. Lien was dragged out and then beaten and stomped by on by at least six motorcyclists. A good Samaritan intervened, but motorcyclists also slammed the back seat windows, where the baby was sitting.

Braszczok waited until three days after the beating—Wednesday, October 2—to disclose he had been at the race, but had claimed he only witnessed the attack while on the off-duty ride. The AP reports, "But investigators discovered video evidence showing him punching an already damaged back window, then twice kicking the side of the SUV before leaving the scene, according to two people familiar with the case. The people weren’t authorized to discuss the inquiry and spoke to The Associated Press on the condition of anonymity."

According to the Post, "The cop also said he feared for his life if he blew his cover in any way — but law-enforcement sources scoffed at the claim. He works undercover narcotics, but is on assignment with the NYPD’s Intelligence Division and wasn’t on the clock at the time." A source said, "He totally lied when he said he did nothing because he didn’t want to blow his cover." The Post adds, "If he caused $1,500 or more in damage to Lien’s car, Braszczok faces a D felony, which carries up to seven years. The Range Rover’s rear window costs $1,730."

The detective did not attack Lien; a Daily News source explained, "Once the beating starts, you can see him hop on the bike and take off. So he’s not involved in the assault, but he lied. He wasn’t truthful." He also didn't help the victim! Still, the Wall Street Journal reports, "IAB investigators want to add additional charges against Mr. Braszczok and prosecutors are trying to determine if the evidence was there to support the charges, the official said."

The video that allegedly shows Braszczok beating in the window has not been made public yet. As for his OWS days, NBC New York says, "During his time with Occupy Wall Street, he participated in demonstrations, attended meetings and essentially lived like a protester to provide information to the NYPD, according to the official."

Braszczok, who is now on modified duty, no longer has a Detectives Endowment Association union lawyer; his new lawyer is John Arila. Detectives Endowment Association President Michael Palladino said to the WSJ, "I'm going to withhold any comment at this time."