WASHINGTON: The head of the US Secret Service faced scathing criticism on Tuesday for the agency allowing an intruder with a knife to run into the White House, while details emerged of a separate security lapse involving an armed contractor who rode an elevator with President Barack Obama. Secret Service Director Julia Pierson acknowledged the agency charged with protecting Obama had failed on Sept. 19 when it allowed a man to jump the fence at the home of the president, burst through the front door and run about 130 feet (40 meters) into the East Room, which is used for events and receptions. "This is unacceptable and I take full responsibility," Pierson told a US House of Representatives committee. "We are all outraged within the Secret Service at how this incident came to pass. It is self-evident mistakes were made," she said, promising lawmakers that it would never happen again. As a first step, Pierson said the front door of the White House now has an automated lock when there is a security breach. It did not have one at the time of the intrusion. Any disciplinary actions, however, would be based on an internal probe by the agency, Pierson said. The incident was another black mark for the Secret Service, which has suffered a series of scandals including a lone gunman firing shots at the White House in 2011, a prostitution scandal involving agents in Colombia in 2012 and a night of drinking in March that led to three agents being sent home from a presidential trip to Amsterdam. In another security lapse for the agency, a private security agent who had a gun shared an elevator with Obama in Atlanta on Sept. 16, three days before the White House intrusion, a Secret Service official said. The man, who was operating an elevator carrying Obama and his Secret Service detail during the president's visit to the US Centers for Disease Control and Prevention, aroused suspicion when he began taking pictures and video of Obama on his phone, the official said. During questioning, the man's supervisor asked for his gun, startling Secret Service agents. Under agency rules, people with access to the president need special clearance to carry guns. The Washington Post, which along with the Washington Examiner, first reported the incident, said the man had three convictions for assault and battery. House Oversight Committee Chairman Darrell Issa, a Republican, said an internal probe was insufficient to rebuild trust in the agency. US Representative Michael McCaul, chairman of the House Committee on Homeland Security, said he would introduce legislation to create an independent commission to conduct a top-to-bottom review of the agency. In a hearing of more than three hours, lawmakers criticized Pierson's initial post-incident statement, which made it appear intruder Omar Gonzalez was apprehended just inside the door. But she acknowledged on Tuesday that Gonzalez, an Iraq war veteran, struggled with an officer inside the door and crossed through a large foyer into a hallway and most of the way through the 80-foot (24-meter) East Room. Shortly before the intrusion, Obama and his family had left for the weekend. 'HOW ON EARTH DID THIS HAPPEN?' Gonzalez will return on Wednesday to federal court, where he has been charged with unlawful entry while carrying a weapon. A federal grand jury indicted him on Tuesday on that federal offense, along with District of Columbia charges of carrying a dangerous weapon outside a home or business and unlawful possession of ammunition. "The White House is supposed to be one of America's most secure facilities," Issa said. "How on Earth did this happen?" Another Republican, US Representative Jason Chaffetz, pressed Pierson on when officers can use lethal force against intruders in a modern era of suicide bombers. She said such decisions were up to officers, but they first need to determine that they or others are in imminent danger. Chaffetz told Pierson: "I want it to be crystal clear. You make a run and a dash at the White House, we're gonna take you down. I want overwhelming force. Do you disagree with me?" Pierson replied, "I do want officers and agents to execute appropriate force for anyone intending to challenge and breach the White House." White House spokesman Josh Earnest said Obama had confidence in Pierson and said she did not offer her resignation. Pierson said the Secret Service had apprehended 16 fence jumpers in the last five years, including six this year. On Sept. 11, someone was caught seconds after scaling the fence. Lawmakers questioned why Gonzalez had escaped more scrutiny. In July, he was arrested in Virginia for reckless driving, eluding police and possessing a sawed-off shotgun. In August, he was stopped, but not arrested, while walking along the south fence of the White House with a hatchet in his waistband. Pierson said the agency was down about 550 employees from its optimal level, and there had been staff reductions following automatic spending cuts and "other fiscal constraints." Obama appointed Pierson, 55, a 30-year Secret Service veteran, in March 2013. The first female director in the agency's 148-history, she was given the mission of cleaning up the agency's culture.