An apparent Halloween misunderstanding threw the Capitol into chaos this afternoon as Capitol Police officers guarding the Cannon House Office Building triggered a massive, sometimes confusing, search for what they believed was an intruder armed with a gun.

One hour and forty-five minutes after it began, police announced that the situation was resolved and that the gun spotted on a X-ray machine was actually a toy.

Capitol Police Chief Terrance Gainer called it “an unusual set of Halloween circumstances,” adding that “there was no ill intent.”

In the end, the police said the incident was in fact sparked by a female staffer bringing a Halloween costume that included a plastic gun into the building. The staffer apparently turned herself into police.

The outcome was a relief to those who recalled the July 1998 shooting at the Capitol that left two officers dead, but questions were immediately raised about the adequacy of the department’s response to this scare. Capitol Police spokeswoman Jessica Gissubel said the toy gun was definitely a weapon, a statement that later turned out to be inaccurate.

The Containment Emergency Response Team — the Capitol Police’s version of a SWAT team — had begun conducting a floor-by-floor sweep for the suspect and another woman an hour after the incident first began. Dozens of officers surrounded the entrances to Cannon as the manhunt continued, blocking anyone from getting in or out of the massive building, home to roughly 140 Members.

Basement tunnels leading to the Capitol and the Longworth Building were sealed off, and other, unspecified “security procedures” were triggered as well, according to House Administration Chairman Bob Ney (R-Ohio).

The incident sparked a storm of chaos among Members and staffers. Initial reports said a male suspect, entering Cannon through its southeastern door at approximately 1 p.m., placed a backpack on the conveyor belt used for the X-ray machine. The man was described as about 5 feet 3 inches tall and 140 pounds and wearing a black suit, who then supposedly passed through a metal detector himself. A large crowd was passing through the building entrance at that time.

When officers guarding the door saw the outline of a gun on the X-ray machine, the suspect reportedly snatched the backpack off the machine and fled into the building, setting off the massive search.

Gissubel later said that police were also looking for a 20- to 25-year-old woman as well, although Gissubel would not say how the two were linked.

Several sources inside Cannon described the scene as one of total confusion, with Capitol Police first locking Members, staff and visitors into their offices, then throwing open the doors and telling for everyone to evacuate.

But when those inside tried to leave the building, an announcement came over the public-address system ordering them back to their offices.

“It was totally screwed up,” said one House staffer trapped inside Cannon. “No one knew what the hell was going on — not us, not the cops, nobody.”