Pittsburgh, PA – Undercover Pittsburgh detectives investigating reports of narcotics sales at Kopy’s Bar ended up in a brawl with several armed members of the Pagans motorcycle gang early Friday morning (video below).

The fight broke out just after 1 a.m., when a bar patron recognized the four undercover detectives and blew their cover, WTAE reported.

“Those guys are cops,” the customer told six alleged Pagans motorcycle gang members inside the bar, according to the New York Post.

According to a report written by Pittsburgh Detective Brian Burgunder, one of the detectives approached the bikers when he realized what the customer had said.

“[He] confirmed to them that we were, in fact, police officers and we were not there to infringe on anyone’s good time,” the criminal complaint read, according to the New York Post.

Two of the Pagans left the bar, while the other four conversed cordially with the detectives and shook their hands several times.

But the interaction rapidly turned violent when one of the bikers, 36-year-old Frank Deluca, suddenly began screaming at the detectives and shoved one of them.

Another Pagans member, six foot three inch, 280-pound Michael Zokaites, then allegedly punched two of the detectives in their faces and heads before he was tackled to the ground by another detective.

When Det. Burgunder grabbed on to Deluca, he realized the biker had a handgun on his waistband and alerted his fellow officers.

Despite the detectives’ commands, Deluca continued to throw punches and kick the officers, cell phone footage showed.

“I’m a cop! I’m a cop!” one of the detectives yelled. “What the f–k is wrong with you?”

The detectives had requested backup when the realized their cover was blown, and a responding sergeant deployed pepper spray to break up the altercation, the New York Post reported.

The detectives and the bikers were all hit by the spray.

At least one other officer deployed a Taser to quell the melee, WTAE reported.

Officers delivered several strikes to Deluca’s face, and were ultimately able to take him into custody, according to the New York Post.

He was taken to a local hospital for treatment of his injuries prior to being booked into jail.

Handguns were seized from Deluca and another biker, 28-year-old Erik Hertzrater.

Investigators confirmed that the men both had concealed weapons permits.

Police also recovered three “large” knives from the floor of the bar after the violent altercation, the Pittsburgh Tribune-Review reported.

Deluca, Hertzrater, Zokaites, 38, and 61-year-old Bruce Thomas were all arrested for aggravated assault, conspiracy, and riot.

But according to Pittsburgh Citizen Review Board Executive Director Beth Pittinger, cell phone footage of the brawl has prompted the board to open an investigation into the detectives’ actions, WTAE reported.

“Those video clips standing alone can be very inflammatory, which can have a very negative and disruptive effect on the community-police relationship,” Pittinger told the news outlet.

She also criticized one of the detectives for using vulgar language during the brawl with the biker gang.

“It was fairly course and there was a lot of anger shown by people who identified themselves as police officers,” she said. “We only know part of it, but that little part out there could be very destructive.”

According to WTAE, the bar owner denied that illegal drug activity has been taking place in or around the bar, and said he has turned surveillance footage of the altercation over to investigators.

You can watch cell phone footage of the detectives’ altercation with the biker gang members in the video below: