Gov. Chris Christie on Thursday apologized to the people of New Jersey, as he announced he fired aide Bridget Anne Kelly for her role in a growing scandal about whether lane closures on the George Washington Bridge were political payback.

"I am embarrassed and humiliated by the conduct of some of the people on my team," Christie said, adding that he is "sick over this."

There is "no doubt in my mind the conduct exhibited is completely unacceptable and shows the lack of respect for the appropriate role of government and the people we are trusted to serve," Christie said.

Christie, sounding chastened at times, insisted he did not know about the actions of his aides and appointees. He said it was "obvious" that Kelly had lied to him when he asked staff to disclose whether they had any knowledge of the traffic jams that occurred last fall.

The governor also asked Bill Stepien, his campaign manager, to withdraw his name as leader of the state Republican Party.

"I had no knowledge or involvement in this issue in its planning or its execution," Christie said. "I am stunned by the abject stupidity shown here. Regardless of what the facts ultimately uncover, this was handled in a callous and indifferent way."

The scandal engulfs Christie as he raises his national profile as the leader of the Republican Governors Association and possibly prepares

for a 2016 bid for his party's presidential nomination. He has consistently been at the top of early presidential polls on potential GOP candidates, and parlayed his image as a tough-talking politician to easily win a second term as governor.

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Christie's comments came amid news reports the U.S. attorney will launch an investigation into the matter. A state investigation is already underway.

Several news organizations obtained copies of the communication between Kelly, then Christie's deputy chief of staff and David Wildstein, a Christie appointee at the Port Authority of New York and New Jersey, that indicated they schemed to cause delays on the heavily traveled bridge. Messages from Stepien were also in the mix.

Before Christie's news conference, State Sen. Ray Lesniak, D-N.J., called for a federal investigation by the U.S. attorney's office. U.S. Sen. Jay Rockefeller, D-W.Va., had already asked the federal Transportation Department to look into the matter.

"There's certainly reasonable suspicion that criminal acts have been involved here," Lesniak, a Democrat, said on CNN's New Day. "Not only abuse of governmental power for political purposes, but we have reckless endangerment of people's lives and possibly criminally negligent homicide."

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Wildstein, a top Christie appointee at the Port Authority of New York and New Jersey, is scheduled to testify later today before a state Assembly transportation committee.

Wildstein, a high school friend of the governor, resigned in December. He was the recipient of a message in August from Kelly, who wrote,"Time for some traffic problems in Fort Lee." Weeks later, Wildstein closed two of the three lanes connecting Fort Lee to the heavily traveled George Washington Bridge.

Pleas from Fort Lee Mayor Mark Sokolich went unheeded as the traffic jams continued. Sokolich, a Democrat, did not endorse Christie for re-election, during a campaign in which he stressed his ability to work across the aisle with political rivals.

The bridge delays reportedly slowed emergency workers trying to respond calls, according to The Record. The Bergen, N.J., newspaper reported one of those calls involved an unconscious 91-year-old woman, who later died.