Matthew Rodriguez, 28, who works for the NYPD's Internal Affairs Bureau, came forward a few days ago to confess he was among those from the NYPD present at last month's violent bike incident, sources said. View Full Caption Twitter

NEW YORK — Another NYPD officer has come out of the shadows to admit he was riding with the motorcycle road-rage mob that attacked a Manhattan dad — and he works for the department’s Internal Affairs Bureau, DNAinfo New York has learned.

Matthew Rodriguez, 28, a five-year veteran who was assigned to the IAB's command center about a month ago, quietly came forward a few days ago to confess he was among those from the NYPD present at last month's violent bike incident — to the shock of his supervisors, sources said.

The IAB is responsible for monitoring wrongdoing by fellow officers and is currently investigating those involved in the same SUV attack the IAB officer was allegedly a part of.

It wasn't immediately clear whether he has been personally involved in the SUV investigation.

The NYPD did not immediately respond to calls for comment.

Rodriguez' lawyer, Pat Bonanno, declined to comment, saying only that his client hasn't been charged with any wrongdoing and is still assigned on full duty to the IAB.

Source said Rodriguez has not been removed pending a decision whether he'll be grilled by the police department or sent straight to a grand jury.

Rodriguez, who recently moved with his family from the Bronx to a home in upstate New York, was a known bike aficionado who talked about selling a motorcycle before the move because his wife didn't like it, according to a neighbor.

He also maintained a Twitter feed with a background image of a man and woman copulating on the back of a motorcycle under the headline "No Free Rides! Gas or A--!"

The revelation is another black eye for the NYPD coming the same week as Detective Wojciech Braszczok, an undercover officer in the Intelligence Division, was arraigned on felony assault, gang assault and riot charges for being involved in the Sept. 29 chase and attack on 33-year-old Alexian Lien.

READ DNAINFO WHO'S WHO IN THE CLASH BETWEEN BIKERS AND ALEXIAN LIEN

Sources say he clearly faces serious disciplinary action within the NYPD for failure to come forward for nearly two weeks, including obstructing governmental administration and official misconduct, sources said.

He could also face a criminal charge for failing to intervene in the attack that ended with Lien being dragged out of his Range Rover and beaten, kicked and stomped by a gang of motorcyclists in front of Lien's wife and 2-year-old daughter, sources said.

DNAInfo has previously reported that as many as six NYPD officers were riding with the horde of motorcyclists up the West Side Highway.

In addition to Braszczok, “On The Inside” was the first to report that another off-duty NYPD detective, Samir Gonsalves, 34, was among the motorcyclists. Gonsalves was arrested recently after allegedly fighting with officers who turned up to break up an alcohol-fueled domestic spat between him and his girlfriend, who works for the Queens District Attorney's office.

Gonsalves has said he did not witness the beating of Lien. The NYPD has not said what, if any, action has been taken against him in connection to Lien's beating.

Like Rodriguez, Braszczok, 32, also waited several days before coming forward to admit his involvement — and even then gave conflicting reports, police said.

Three days after the attack, Braszczok told investigators he was riding with the mob, but took no action to stop the beating because he came upon the beat-down as it ended.

He also said he feared blowing his undercover, which DNAinfo New York disclosed involved infiltrating Occupy Wall Street protesters before the NYPD crushed their Zuccotti Park encampment in 2011.

But prosecutors say Braszczok was caught on photos and video pounding on Lien’s car moments before the young dad was yanked from the driver's seat of his SUV, badly beaten and stomped.

Manhattan Assistant District Attorney Samantha Turino said Braszczok was an “active participant” and “did nothing to stop it, including not calling 911.”

Lien suffered black eyes and required stitches to close several facial lacerations.

On that fateful day, Lien was celebrating his wedding anniversary with his wife and child with a drive on the West Side Highway when his SUV was surrounded by scores of motorcyclists.

Lien bumped the back of one of the motorcycles, angering fellow bikers who began pounding on his SUV with their helmets and slashing his tires, police said. Lien hit the gas to get away and drove over three bikers, including one who was critically injured, police said.

Furious motorcyclists pursued his Range Rover up the Henry Hudson Parkway until they caught up with him on West 178th St., where Lien was again surrounded and his car smashed. He was dragged to the pavement and assaulted before good Samaritans stepped in.

Video recorded on a motorcyclist’s helmet camera captured much of the action and went viral on the web.

The identities of any other officers who were riding that afternoon have yet to surface.

Seven other bikers have been arrested and charged in connection with Lien’s beating. Authorities are looking for several more bikers.

Additional reporting contributed by Tom Liddy, Mat Katz and Ben Fractenberg