From WaPo:

The man who jumped over the White House fence and sprinted through the main floor of the mansion could have gotten even farther had it not been for an off-duty Secret Service agent who was coincidentally in the house and leaving for the night.

The agent who finally tackled Omar Gonzalez had been serving on the security detail for President Obama’s daughters and had just seen the family depart via helicopter minutes earlier. He happened to be walking through the house when chaos broke out and the intruder dashed through the main foyer, according to two people familiar with the incident.

Gonzalez, 42, was the first person in modern memory to jump over the White House fence and get into the mansion, largely the result of a failure of numerous layers of Secret Service security on the northern fence line.

Though the Secret Service initially said that Gonzalez was quickly detained inside the front door, The Washington Post reported Monday that the man actually made it well into the house before he was tackled on the far southern side of the 80-foot-long East Room.