32-year-old Clint Caldwell of Brooklyn has been arrested for gang assault, assault, and criminal mischief.
Caldwell is allegedly one of the motorcyclists involved in the assault on Lien once the SUV stopped in Washington Heights.
Caldwell was not caught on the six-minute video that was posted on YouTube. Caldwell allegedly helped pull Lien out of the SUV and then assaulted him.
The undercover officer is 32-year old Detective Wojciech Braszczok, a 10-year veteran of the NYPD. He is charged with riot and criminal mischief.
Braszczok spent much of his police career in narcotics but recently transferred to another division.
Internal Affairs had been reviewing his load of former narcotics cases as charges against him were being contemplated.
Prosecutors planned to arrange his surrender over the next 48 hours but Internal Affairs investigators believed they had enough evidence to make the arrest and told his attorney to bring him in. Additional charges are possible as the investigation continues.
Braszczok was already under scrutiny for not immediately reporting the assault to Internal Affairs and not being immediately entirely forthcoming when he did. But investigators say the determining factor in moving forward with charges was newly acquired video that showed he vandalized the victim's SUV by breaking the rear hatchback window, an act that contradicted his prior accounts in which he claimed he drove away without taking any action to avoid blowing his cover.
Investigators believe that while Braszczok was one of three officers on the ride in the general area of the attack, he was the closest to the beating and the only one to have a clear view of what was happening. They believe another detective was further away from the attack and a third, an officer, was "in the way back" of the motorcycle pack.
The other two officers conduct is still being probed, but investigators said they are not expected to face criminal charges.
Sources say a second detective is also believed to have been among the riders, but not present for the attack. That detective is already on modified duty after being arrested in August during a domestic dispute at an intersection in Queens. The criminal complaint says the cop went after a responding officer: "He shoved him in his chest several times in a forceful manner." The charges will be dismissed if the detective stays out of trouble for six months.
"We are looking at all aspects of this investigation," Kelly said.
Another video that's emerged in the case shows SUV driver Alexian Lien on the ground in Washington Heights, surrounded by a mob. CLICK HERE to see the full video on YouTube.
In addition, police released the photos of 4 more suspects wanted for questioning in the assault. VIEW THOSE PHOTOS
A grand jury hearing is evidence against in the assault cases already filed. That will include the victim making a statement for prosecutors.
Meantime, a fourth suspect has been arraigned on multiple charges related to the incident.
On Tuesday, 29-year-old Craig Wright became the fourth motorcyclist arraigned in connection with this incident. He pleaded not guilty to charges of assault, gang assault and unlawful imprisonment and was ordered held on $100,000 cash bail/$150,000 bond.
Prosecutors alleged that Wright punched Lien through the window of the SUV and then kicked him while he was on the ground.
He is due back in court on October 11.
Sources say police tracked down Wright by the license plate on the motorcycle, which belonged to his uncle.