a pack of motorcyclists descended upon New York City and attacked a young family in their car, dragging the driver from his seat and beating him. Making matters worse, the New York Post reported Friday that an off-duty, undercover NYPD officer was riding with the bikers. He did not interfere with the beating, because, according to a law-enforcement source, “he didn't want to blow his cover.” The undercover officer came forward Wednesday night and has since lawyered up. None of the bikers who assaulted the SUV driver are under arrest -- and new photographic evidence suggests that as many as five bikers attacked the driver while his wife and 2-year-old were in the car.

One of those bikers was allegedly Robert Sims, 35, of Brooklyn. He was taken into custody Friday afternoon and charged with gang assault, assault, criminal possession of a weapon, attempted assault and attempted gang assault, a source told the New York Post. “Apparently he hit the guy.”

"Besides Sims only one other biker has been charged in the rampage despite videos, still photos and non-biker witness accounts from the broad-daylight attack.

Christopher Cruz, 28, of Passaic, NJ, faces misdemeanor charges of reckless driving and imprisonment for suddenly slowing his bike in front of the Range Rover, causing the fender-bender blamed for sparking the chase and violence.

Meanwhile, the only biker injured during the rampage threatened he may sue Lien for running him over with the Range Rover when he hit the gas as his SUV was first surrounded.

“He was attempting to diffuse the situation,” lawyer Gloria Allred said of Edwin Mieses, 32, whom she said may be paralyzed from the waist down “for the rest of his life.”

Mieses hasn’t had a valid license in his home state of Massachusetts since 1999, and haas never applied for a motorcycle license."

The New York Daily News reports that Undercover and off-duty cops were among the bikers that chased Lien and his family, and did nothing to stop the attack on Lien.

An undercover NYPD detective, afraid of blowing his cover, watched an angry motorcycle mob terrorize a defenseless man out for a drive with his wife and their 2-year-old daughter, the Daily News learned Friday.

The off-duty officer was one of two detectives riding Sunday with the motorcyclists who yanked Alexian Lien from his Range Rover and inflicted a beatdown near W. 178th St. in front of the driver’s family, a source told the Daily News.

The police source said the detective was not investigating anyone on the ride, but thought he could "pick up some tips about criminal activity."

The detective reportedly left once he knew police were on their way and people had rushed to aid Mr. Lien.

Neither of the officers informed their superiors that they attended the biker ride for several days.

The detective told colleagues he didn’t want to end up like Detective Gescard Isnora, an undercover police officer involved in the shooting of Sean Bell, the source said. Isnora stepped out of his undercover role, firing the first shot as four other officers blasted the unarmed Queens man on his wedding day with a hail of 50 bullets in 2006. Isnora -- along with the other officers involved -- was fired, lost his pension and health benefits for shooting his weapon while undercover.