The Washington Post reports that Omar Gonzalez, the Iraq veteran armed with a knife who jumped over the White House fence on Sept. 19, overpowered a Secret Service agent at the building's front door and sprinted into the East Room before he was subdued—directly contradicting the Secret Service's statements that Gonzalez had been apprehended immediately after entering the premises.
After barrelling past the guard immediately inside the door, Gonzalez, who was carrying a knife, dashed past the stairway leading a half-flight up to the first family’s living quarters. He then ran into the 80-foot-long East Room, an ornate space often used for receptions or presidential addresses.
Gonzalez was tackled by a counter-assault agent at the far southern end of the East Room. The intruder reached the doorway to the Green Room, a parlor overlooking the South Lawn with artwork and antique furniture, according to three people familiar with the incident...
Secret Service officials had earlier said he was quickly detained at the main entry.
Here, from C-SPAN, is the relevant floor plan:
Gonzalez entered the building through the North Portico.