10/08/2013 10:32 am ET Updated Oct 08, 2013

NYPD Biker Cop Attacked SUV, According To Report; Another Suspect Arrested In Assault

An undercover NYPD narcotics cop has been identified as one of the motorcyclists who attacked a Range Rover in Manhattan last week. The unidentified cop, who initially claimed to have taken no part in the brutal beating of the SUV's driver, Alexian Lien, can be seen in an unreleased video hitting his fists against the vehicle, sources tell The New York Post.

The seven-year veteran of the force has been placed on modified duty and has turned in his gun and badge. He may not, however, face criminal charges over the incident. The decision last week by the Manhattan District Attorney's office not to prosecute 43-year-old Allen Edwards, who allegedly smashed the SUV's windows, hampers the DA's ability to go after the undercover cop.

DNAinfo reported Friday that out of six off-duty NYPD cops who happened to be taking part in the group motorcycle ride on September 29, none intervened during Lien's beating. From DNAinfo:

Internal affairs has the names of two detectives, one sergeant and three police officers who were either on the highway when motorcyclists confronted Lien, who was driving with his wife and 2-year-old daughter, or witnessed the assault at West 178th Street, according to sources.

Another biker was arrested on Monday. 29-year-old Craig Wright was cuffed in Brooklyn, The New York Daily News reports. Wright, who was charged with gang assault, can allegedly be seen in a new video punching Lien through the smashed window of the SUV.

Wright's arrest brings the total number of arrests over the SUV attack to four. 37-year-old Reginald Chance was charged with gang assault over the weekend. 35-year-old Robert Sims was also charged with gang assault. And 29-year-old Christopher Cruz-- whose initial confrontation with Lien on the West Side Highway is thought to have set off the high-speed chase and the ensuing Washington Heights assault-- was charged with reckless endangerment. Cruz spoke to ABC this week, characterizing portrayal of the story as "unfair," and added that his life had been turned "upside down."

Another disturbing detail emerged this week surrounding the assault. According to a witness, Lien's wife, Rosalyn Ng, was also attacked during the incident. One of the motorcyclists started to drag her from the car until bystanders yelled at him to stop. A new photo revealed that the passenger-side window of the SUV was also smashed.

Edwin Mieses--the motorcyclist run over by the SUV as Lien sped away from bikers on the highway-- suffered two broken legs, bruised lungs, and spinal fractures.