A Canadian soldier standing guard at a war memorial in the country's capital was shot to death Wednesday, and gunfire then erupted inside Parliament, authorities said.
One gunman was killed, and police said they were searching for as many as two others in what Gilles Michaud, assistant commissioner of the Royal Canadian Mounted Police, called a "dynamic, unfolding situation.''
The Ottawa police, via its official Twitter account, warned the public to stay away from that area while it investigated.
The Maple Leafs were on lockdown earlier Wednesday at the team's hotel in downtown Ottawa, a team representative confirmed to ESPN.com. A team spokesman said the Maple Leafs were scheduled to leave Ottawa later in the afternoon.
The NBA's Toronto Raptors, meanwhile, said they were working with local police to have extra security in place for their preseason game at home Wednesday night.
The Leafs were scheduled to play the Senators at 7 p.m. ET, at the Canadian Tire Centre in nearby Kanata. The date and time of the rescheduled game have not been announced.
"The National Hockey League wishes to express its sympathy and prayers to all affected by the tragic events in Ottawa," the league said in a statement announcing the postponement.
Senators owner Eugene Melnyk echoed those sentiments.
"We are shocked and deeply saddened by today's tragic events on Parliament Hill and in downtown Ottawa," 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."
Maple Leafs forward Joffrey Lupul described the scene on Twitter.
One player, via text to ESPN.com's Pierre LeBrun, said he and his teammates are following the situation and remain in disbelief: "Terrible day."
"We have been witness today to some terrible events but are thankful to those brave men and women for their tireless service in protecting everyone's safety," the Maple Leafs said in a statement.
The Leafs, who played the Islanders on Tuesday night in New York, did not have a morning skate at Canadian Tire Centre.
Information from ESPN.com's Pierre LeBrun and The Associated Press was used in this report.