The spate of shootings in Ottawa has had a major ripple effect in Canada and the United States, triggering responses from the North American Aerospace Defense Command, the U.S. State Department and the National Hockey League.
A Canadian soldier standing guard at a war memorial in the country's capital was shot to death and heavy gunfire then erupted inside Parliament. One gunman was killed, and police said they were hunting for as many as two others.
After the incident, the State Department announced that the U.S. Embassy in Ottawa was on lockdown.
"Our thoughts and prayers are with the victims and their families," said State Department Deputy Spokeswoman Marie Harf. "We have full confidence in Canadian law enforcement officials."
Harf said Secretary of State John Kerry, who was on his plane on the way back from Berlin, has been briefed on the situation and is following it closely.
Security was also tightened at the Tomb of the Unknown Soldier at Arlington National Cemetery just outside Washington, a spokesman at the cemetery said.
In a statement, the FBI said there is no evidence indicating there is a threat to the U.S. but, in light of the Ottawa shootings, the bureau has told its field offices and government partners "to remain vigilant in light of recent calls for attacks against government personnel by terrorist groups and like-minded individuals."
The FBI said the NYPD has extra security at the Canadian consulate in Manhattan.
A Department of Homeland Security official said the U.S. is monitoring the situation.
In addition to the U.S. Embassy, numerous other locations were put on lockdown throughout Ottawa, including the Chateau Laurier Hotel, National Arts Institute, City Hall, World Exchange Plaza, Place de Ville office towers and Rideau Shopping Center.
CBS News correspondent David Martin reports that NORAD, which is a joint U.S./Canadian command, is putting fighter aircraft on a higher alert to be ready to respond to an air incident in Canada. The higher alert could involve more aircraft on strip alert, putting aircraft into combat air patrol orbits or moving fighters to bases from which they could more quickly respond.
Officials also canceled two events in Toronto honoring Pakistani teenager and Nobel laureate Malala Yousafzai, including one in which she was supposed to receive honorary Canadian citizenship. The teenager was shot in the head by a Taliban gunman in 2012 for calling for schooling for girls.
Meanwhile, the NHL postponed Wednesday night's game between the Toronto Maple Leafs and Senators because of the shootings.
The NHL said in a statement it "wishes to express its sympathy and prayers to all affected by the tragic events in Ottawa."
The game was scheduled at the Canadian Tire Centre in nearby Kanata.
"We are shocked and deeply saddened by today's tragic events on Parliament Hill and in downtown Ottawa," Senators owner Eugene Melnyk said in a statement. "Our collective thoughts and prayers are with the families of the victims as well as with all members of Parliament and staff who have had to manage through today's difficult circumstances.
"Hockey is certainly secondary to these types of tragic events and we know our fans stand alongside us with the league's decision to postpone tonight's game."
The NHL said the date and time of the rescheduled game will be announced at a later date.