Secret Service chief RESIGNS after knife- wielding intruder breached the White House and armed man got into President's elevator over just three days  

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Julia Pierson, the first woman to helm the U.S. Secret Service, resigned on Wednesday following two embarrassing episodes over just three days that underscored the once-respected agency's struggle to protect the president and the White House.

A bitter Pierson gave an exit interview in which she claimed resigning with her agency in tatters was 'the noble thing to do,' and blamed news outlets for the quick collapse of her job.

'The media has made it clear that this is what they expected,' she told Bloomberg News. 

Pierson faced a hostile panel of lawmakers on Tuesday who demanded a better showing from the nation's top bodyguards after a mentally ill veteran scaled the White House fence on Sept. 19 and scampered more than 100 feet into the building, with a knife in his pocket, before agents tackled him.

'It's unacceptable,' Pierson conceded, but even President Obama's allies would hear none of it.

'I wish to God you protected the White House like you protected your reputation here today,' Massachusetts Democratic Rep. Stephen Lynch barked at her.

Hot seat: Julia Pierson absorbed endless flak from Republicans and Democrats alike on Tuesday during a contentious Capitol Hill hearing

Guarded: Pierson had her own personal protection detail when she arrived to testify before Congress on Tuesday

Shortly after the hearing, news emerged that on Sept. 16 an armed private security guard was allowed on an elevator with President Obama during his visit to the Centers for Disease Control and Prevention in Atlanta. His Secret Service detail wasn't aware the man was carrying a gun.

Calls for Pierson's ouster began to filter out to reporters within hours, beginning with Maryland Democratic Rep. Elijah Cummings, who walked back that demand on Wednesday morning.

By then, however, House Minority Leader Nancy Pelosi had jumped on a moving train and said Pierson should step down. 

Several other members of Congress, mostly in the Senate, had insisted on the formation of a blue-ribbon panel to probe the Secret Service's lapses. Those demands are not likely to quiet down even after Pierson's replacement is chosen.

California Republican Rep. Darrell Issa, who chairs the House Oversight and Government Reform Committee – the site of Tuesday's legislative bloodbath – said Wednesday that the resignation 'does not resolve' all the Secret Services's problems, some of which 'pre-date Ms. Pierson’s tenure as director.'

'Yesterday, the Committee called for an outside review by independent experts,' he said. 'Today, Homeland Security Jeh Johnson today agreed that such a review is critical.' 

Pierson told Bloomberg that it was 'in the best interest of the Secret Service and the American public if I step down. Congress has lost confidence in my ability to run the agency. The media has made it clear that this is what they expected.'

'I can be pretty stoic about it, but not really,' she said. 'It's painful to leave as the agency is reeling from a significant security breach.'

That breach outraged Sen. Tom Carper, a Delaware Democrat who chairs the Homeland Security Committee in the upper chamber of Congress.

He said an 'obvious dissonance that exists within an agency' was apparent because it could 'secure an event with over 100 world leaders at the United Nations General Assembly in New York City for nearly three weeks without apparent incident, but simultaneously fail to keep an intruder from running into the White House.'

Obama appointed Pierson last year as pushback against perceptions that the service was becoming a boys'club.

About 90 per cent of the 3,500 agents are male, and some of them were caught engaging prostitutes during an advance trip before Obama's 2012 trip to the South American nation of Colombia.

Having a woman at the helm was thought to be a salve for the agency's suddenly scandalized public image.  

A veteran with PTSD scaled a White House fence on Sept. 19 and made it 168 feet into the presidential mansion before an off-duty agent happened to see him and brought him to the ground

White House Press Secretary Josh Earnest told reporters on Wednesday that the president and his inner circle were unaware of the elevator lapse at the CDC until 'just minutes' before the Washington Examiner broke the story Tuesday afternoon.

Earnest wouldn’t say whether Pierson herself told Obama, or the White House learned of it from the media. 

But 'my only knowledge of this is based on public reports,' Earnest admitted. 

Utah Republican Rep. Jason Chaffetz claimed in an interview with The Washington Post that the man on the elevator was a convicted felon, but a Secret Service source later told the Fox News Channel that he was never prosecuted following an arrest for Assault and Battery. 

'You have a convicted felon within arm's reach of the president and they never did a background check,' an angry Chaffetz said. 'Words aren't strong enough for the outrage I feel for the safety of the president and his family.'

'His life was in danger. This country would be a different world today if he had pulled out his gun.' 

The man, a private security guard, was stopped for questioning because he refused to stop taking a cell-phone video of the Obama during the elevator ride.

His supervisors suspended him on the spot and demanded he turn over his firearm – shocking Secret Service agents who weren't aware he was armed.

Better days: Obama had high praise for the first female Secret Service director when he appointed her less than 18 months ago

Jumper: Omar J. Gonzalez pleaded 'not guilty' Wednesday in federal court, despite video footage of him scaling the White House fence and eluding Secret Service as heran into the president's executive mansion while carrying a knife in his pocket

Earnest said Pierson met Wednesday with Homeland Security Secretary Jeh Johnson, who 'accepted her resignation, which she offered because it 'was in the 'best interest of the agency.'

‘The secretary agreed with that assessment. The president did as well,’ Earnest said. ‘The president concluded that new leadership of that agency was required.’ 

But he wouldn't directly comment on the scandal unfolding over the elevator incident.

Having an armed man in an elevator with the President of the United States was a 'serious breach,' and ‘unwise and unacceptable,’ he said, but he said further comment would have to wait until after an investigation is completed.

'The president has nothing but the highest regard for the men and women of the Secret Service,' Earnest told reporters.

Earnest also wouldn't say whether or not other heads would roll.

But after the Homeland Security Department conducts its own probe, he said, 'the president believes that an independent panel should review the results of this assessment ... to determine what steps are appropriate moving forward.'   

In a statement, Johnson said: ''I salute her 30 years of distinguished service to the Secret Service and the nation.'

Pierson told Bloomberg of her resignation that she had 'met in person' with Johnson, 'and after that discussion I felt this was the noble thing to do' because it would 'take pressure off the organization.'  

Earnest said there is no immediate timetable for Pierson's permanent replacement, which will require Senate confirmation.

And in this corner ... Pierson (center) shook hands with House Oversight Committee chairman Republican Darrell Issa before her dressing-down, as ranking Democrat Elijah Cummings looked on; he would later call for her ouster and then withdraw the demand just hours before Pierson resigned

Joe Clancy, a retired Special Agent, is 'a good candidate for serving as acting director until a more permanent replacement can be found,' Earnest said.

He also revealed that Clancy is taking a 'leave of absence from his private sector job' to run the Secret Service in the interim.

'The president is grateful that he has taken on that very significant responsibility,' Earnest told reporters.

Pierson studied criminal justice at the University of Central Florida and served for three years with the Orlando Police Department. She was among the first female officers assigned to a beat on that force.

She served on the Presidential Protective Detail for President George H.W. Bush, and was put in charge of overseeing protective details for presidents Bill Clinton and George W. Bush.

Moving her up the chain of command made sense on paper in April 2013: Pierson was already serving as chief of staff to then-director Mark Sullivan.

Her working life started in a less-serious way, however. As a teenager in Orlando, she worked at nearby Disney World as a parking lot attendant – and even did a stint in the theme park as a costumed character in parades.

Pierson was still listed on the Secret Service's website as the agency's director as of 3:45 p.m. Wednesday.