UPDATE: 2 dead in Ottawa shootings; security tightened at Arlington, embassy

OTTAWA, Ontario (AP)

A gunman with a scarf over his face shot to death a Canadian soldier standing guard at the nation's war memorial Wednesday, then stormed Parliament in a hail of gunfire before he was killed by the usually ceremonial sergeant-at-arms, authorities and witnesses said.

The attack immediately raised the specter of terrorism, with Canada already on alert because of a deadly hit-and-run earlier in the week against two Canadian soldiers by a man who police say was fired up with radical Muslim fervor.

Police said in the initial hours after the shootings that as many as two other gunmen may have taken part. But as the day wore on, the cordon around Parliament was eased, employees were allowed to go home, and the sense of urgency appeared to wane.

"Today is a sad and tragic day for our city and our country," Ottawa Mayor Jim Watson said. He said it was a tragedy with "origins as yet not fully known, causes not yet fully understood."

Witnesses said the soldier posted at the National War Memorial was gunned down at point-blank range just before 10 a.m. by a man carrying a rifle and dressed all in black, his face half-covered. They said the gunman appeared to raise his arms in triumph, then ran off and entered Parliament, a few hundred yards away, where dozens of shots soon rang out.

People fled the complex by scrambling down scaffolding erected for renovations, while others took cover inside and barricaded doors with chairs as police with rifles and body armor took up positions outside and cordoned off the normally bustling streets around Parliament.

Police gave no details on how the gunman died. But on Twitter, Canada's justice minister and other government officials credited 58-year-old sergeant-at-arms Kevin Vickers with shooting the attacker just outside the MPs' caucus rooms.

Vickers serves a largely ceremonial role at the House of Commons, carrying a scepter and wearing rich green robes, white gloves and a tall imperial hat.

The identity of the gunman was not immediately released, and police would not speculate on a motive for the shootings.

Ottawa Hospital said it received two victims, both listed in stable condition, in addition to the soldier.

Around midday, Ottawa police spokesman Chuck Benoit said two or three gunmen were believed to be involved in the attacks. Gilles Michaud, assistant commissioner of the Royal Canadian Mounted Police, called it a "dynamic, unfolding situation."

In Washington, President Barack Obama condemned the shootings as "outrageous" and said: "We have to remain vigilant." He also offered U.S. help and reassurance in a telephone call with Canada's prime minister.

The U.S. Embassy in Ottawa was locked down as a precaution, and security was tightened at the Tomb of the Unknown Soldier at Arlington National Cemetery just outside Washington.