After days of standing behind Pittsburgh Bureau of Police Chief Nate Harper, Pittsburgh Mayor Luke Ravenstahl abruptly asked for his resignation today, after spending two hours this afternoon being questioned by the FBI and U.S. District Attorney's Office.

In the course of that questioning, Ravenstahl told reporters tonight, he made the decision to ask Harper to step down. Harper has been with the Pittsburgh Bureau of Police for 34 years. He was sworn in as Chief of Police in 2006.

"I learned enough to know it was time for Chief Harper to resign," Ravenstahl said.

Ravenstahl said that following the meeting he called the chief and asked for the resignation by phone. He said no severance package was discussed and whether or not he continues to receive a pension will be up to the pension board. "As of today, he is no longer a city employee," Ravenstahl said.

Harper has not been charged with any crimes.

Despite the federal agents' questioning, Ravenstahl says that he does not believe he is becoming ensnared in the ongoing investigation that has raised questions about mysterious bank accounts, Harper's business relationships with subordinates and the handling of police officers' off-duty work.

"I am not a target," Ravenstahl asserted repeatedly. He said he met with federal authorities at their request this afternoon, but did so voluntarily — without a subpoena.

A personal attorney and a city attorney attended the meeting with him, Ravenstahl said. He declined to name the attorney personally representing him.

Assistant Chief Regina McDonald will become acting chief "indefinitely," Ravenstahl said.

Deputy Chief Paul Donaldson, who served as acting chief recently after Harper took time off following his mother's death, is on vacation now, Ravenstahl said. But he said McDonald is likely to remain in place even after Donaldson's return.

Ravenstahl spokesperson Joanna Doven described the transition details about a half hour before the press conference as "fluid," saying then that Harper's replacement was not yet known. Ravenstahl started the conference nearly an hour after it had been originally scheduled, emerging from meetings on the subject.

Ravenstahl said he has not asked anyone else to resign related to the investigation.

Reacting to criticisms from two of his challengers, City Controller Michael Lamb and City Councilor Bill Peduto, in the upcoming mayoral election, who argued Harper should have been put on leave or fired much sooner, Ravenstahl said he needed more information before making that decision.

"Others without my responsibilities can be quick to judge and make politically expedient statements," he said. "I cannot."

"This had zero to do with politics," he said. "It's a political loser either way."