The White House security report has found that an intruder armed with a knife managed to dodge guards and enter the building because of poor communication and a series of lapses.
Omar Gonzalez jumped over the fence in September, ran past guards and was only stopped deep inside the building.
An official US inquiry says Secret Service agents – including one with an attack dog – did not react on time or in the right manner.
The Secret Service chief, Julia Pierson, resigned, partly as a result of this breach.
She stepped down after details emerged of this incident, and of previous breaches in the security surrounding the president.
The latest findings about the September incident are part of a broader inquiry into the lapses, led by the Department of Homeland Security.
According to The New York Times, an executive summary of the inquiry released on Thursday night said the blame for the breach lay with “performance, organization and technical” failures.
Several lapses were highlighted in the report, pointing to a lack of training, bad staffing decisions and failures in communication.
The report described in detail how agents had missed a series of opportunities to stop Omar Gonzalez – on the evening of the intrusion as well in the run-up to it.
Omar Gonzalez scaled the fence at a point where a spike was missing, the report said.
Many officers at a gate on Pennsylvania Avenue did not have a clear view of him because of a construction project.
An officer with an attack dog on the White House driveway was using his mobile phone at the time, and did not hear warnings on his radio earpiece, or on another radio, which had been stashed away in a locker.
Two officers who were pursuing Omar Gonzalez did not expect him to pass through thick bushes, which he did.
Doors into the White House that officers had assumed were locked turned out to be open. Some officers also hesitated to follow Omar Gonzalez because they did not know the layout of the building, the report said.
Once inside the building, the report said Omar Gonzalez was able to push past a female officer, who was smaller than him and who had accidently reached for her torch instead of a metal baton.
He was eventually tackled in the East Room, a long, ornately-decorated chamber used for presidential addresses and formal receptions.
Early on in the intrusion, warnings were not relayed properly to agents inside the White House building because alarm systems and radios failed to function as intended.
The report also cited failings in the run-up to the intrusion, as the former soldier’s suspicious behavior had attracted the attention of the authorities several times.
Omar Gonzalez was stopped in Virginia in July. Then, officers found two powerful rifles, four handguns and other firearms and ammunition in his vehicle along with a map marking the White House.
President Barack Obama and his family were not at the White House when the intrusion happened, having departed about 10 minutes earlier by helicopter.
Omar Gonzalez has been indicted on charges including unlawfully entering a restricted building or grounds while carrying a deadly or dangerous weapon and unlawful possession of ammunition.
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