The FBI is reviewing a Pittsburgh police detective's arrest of a man outside a South Side bar that prompted the mayor to call for the detective's termination.

“We're currently assessing the situation to determine whether we will look further,” FBI spokeswoman Kelly Kochamba said Tuesday.

A bystander captured a video of Detective Frank Rende's pursuit of Mark Keyser Jr., 27, of Ross with his Taser drawn on Saturday outside Claddagh Irish Pub at SouthSide Works.

Reached by phone, Keyser said FBI agents contacted him through relatives to discuss the incident.

“The FBI told me not to talk to anyone,” Keyser said.

Rende, 55, of New Homestead declined to comment. City police said tests showed Rende did not fire the Taser.

In the video, posted online, Rende unholsters his Taser and taunts people in the crowd before walking away from the camera toward Keyser.

City Solicitor Dan Regan said he was unaware of any FBI investigation related to Rende.

“The only thing I'm aware of is that we're doing a review of the incident, as the mayor said,” Regan said. The city's Office of Municipal Investigations will determine whether Rende violated police policy.

Rende was working off-duty outside Claddagh when a manager asked him to remove a patron, he said in a complaint. Keyser stepped between Rende and the man, he said, and he ejected both men.

The video shows Rende following Keyser down the sidewalk. He shouts, “You want Tased?” and raises his hand with the stun gun while standing next to Keyser, who falls to the ground. Keyser is heard saying: “I tried to leave; you pushed me over.”

Mayor Luke Ravenstahl said on Monday the video showed Rende acting aggressively. “It is very disturbing,” Ravenstahl said.

In 2007, Ravenstahl singled out Rende's involvement in the police union's political action committee when it chose to endorse a Republican candidate for mayor. At the time, Ravenstahl said Rende is “clearly not an ally of mine.”

Rende charged Keyser with defiant trespass, public drunkenness and disorderly conduct. A magistrate released Keyser on a nonmonetary bond.

In his complaint, Rende claims he “placed the Taser to the side of the actor's neck” but did not activate it.

Ravenstahl said he talked with acting Chief Regina McDonald and Public Safety Director Michael Huss about disciplining Rende. He said he wants Rende to be fired but will await results of the internal investigation.

“For the feds to get involved it signals the seriousness, if you will, of what happened on St. Patrick’s Day,” Ravenstahl said. “It’s clear to me that Officer Rende was wrong and needs to be terminated.”

Huss asked McDonald to reassign Rende to the warrant office, an administrative job.

Rende has a history of trouble on the job since his hiring in July 1993.

Another video posted online from an April 2011 arrest at PNC Park shows Rende using a Taser and his baton on Pirates fan Scott Ashley, 43, of Friendship, who pleaded guilty to simple assault, resisting arrest and summary harassment in June 2012.

Ashley claimed this week that a few months after his arrest, the FBI contacted him about Rende's actions. The agency would not confirm that.

“They came to my house,” Ashley said. “They came back again, and gave me a ride to the hospital. They wanted my hospital records. They wanted to investigate his actions.”

Ashley said he didn't hear back from the two agents.

The Citizen Police Review Board reviewed that incident but disposed of the case when Ashley pleaded guilty, Executive Director Elizabeth Pittinger said.

Police investigated Rende for using sick days to perform side jobs but withdrew disciplinary action in 2006, saying he wasn't properly counseled on the city's sick leave policy.

In 1999, Rende responded to a woman's South Side home for a domestic violence report. He returned to the home while off-duty and engaged in a sex act with the woman, according to an OMI report. He was suspended and considered for termination, but an arbitrator reinstated him.

Ravenstahl said he will weigh the South Side incident without taking into consideration Rende's history on the job.

Channel 11's news exchange partners at TribLIVE contributed to this report.