WHITE HOUSE PRESS SECRETARY JOSH EARNEST VIA CBS: "We are confident and the president is confident that the Department of Homeland Security will take a hard look at this situation. ... That will ensure the United States Secret Service can meet the very high standards of performance that they set for themselves."
President Obama has reportedly accepted Pierson's resignation.
She resigned just a day after she appeared before the House Oversight Committee and was slammed over lapses with the Secret Service.
Earlier this week, it was revealed the man who allegedly jumped the White House fence, Omar J. Gonzalez, made his way farther than previously believed.
PIERSON VIA U.S. HOUSE OF REPRESENTATIVES: "The officer then engaged Mr. Gonzalez, they crossed into the East Entrance Hall together, made the left turn down the Cross Hall, they stepped momentarily into the East Room, another officer rendered aid, and he was on the ground on the carpet and handcuffed on the Cross Hall, just outside of the Green Room."
Then there's Tuesday's incident of Mr. Obama riding an elevator with an armed man who had an arrest record.
CNN's Jake Tapper says the White House didn't know about this incident until later and writes, "This is key to understanding why Pierson is out."
Pierson is the second high-profile member of the Obama administration to resign under intense media pressure this year. Eric Shinseki was essentially forced out of his role as Veterans Affairs secretary in May.
The Department of Homeland Security announced Joseph Clancy, formerly special agent in charge of the Presidential Protective Division of the Secret Service, will act as the interim director.
This video includes images from Getty Images.