A manhunt is under way in the Canadian city of Moncton after three police officers were shot dead and two hurt.
Police said they were searching for Justin Bourque, 24, who was "armed and dangerous", and tweeted a picture of a suspect with weapons.
Officials have warned people to stay inside and lock their doors.
The Royal Canadian Mounted Police (RCMP) told the BBC the officers were shot responding to reports of an armed man wearing camouflage clothing.
Prime Minister Stephen Harper has offered his condolences to those affected. "The sacrifice of these brave officers will be honoured and remembered." he said.
Witnesses said they heard the first shots in north-west Moncton at about 20:00 local time (23:00 GMT) on Wednesday. More shots were reported about two hours later.
Police searched through the night and continued their operations at daybreak, with officers combing wooded areas.
The two wounded RCMP officers were taken to hospital and are in a stable condition with non-life-threatening injuries, a police spokesman said.
Officers have blocked off a number of roads in Moncton and traffic is reported to be backed up on major routes across the city. Schools are closed and buses are not running.
The RCMP have released a map of the search area and have asked motorists and pedestrians to stay away.
In a statement, New Brunswick Premier David Alward said he was "shocked and saddened".
"I would ask New Brunswickers, particularly in those areas identified by police, to follow the situation as it develops and to listen to the advice of police," he said.
Moncton's mayor George LeBlanc said: "This is a terrible loss and a tragedy for the families and for all of us here in the city. [We must] pull together as a family to support those who have suffered."
Mr Harper said the incident was "a stark reminder that our men and women in law enforcement put their lives on the line in Canada every day to protect our citizens and communities".
Moncton resident Heidi James told broadcaster CTV that she and her husband had heard four or five shots.
They then saw a "shot-out" vehicle and what looked like a body covered with a blanket, she added.
Eyewitness Danny Leblanc, 42, said he saw the gunman in the distance wearing a camouflage outfit and standing in the middle of the road with a gun pointing at police cars.
He said he believed it was a police officer until he heard a burst of automatic gunfire.
"That guy was standing on the road afterwards and he was looking towards us," he said.
Joan MacAlpine-Stiles told CBC she saw the gunman when she opened a window.
"I said, 'Oh my God, there he is with camouflage and the headband and a gun, and it looked like a bow he had with him. And I mean he was just through our backyard.'"
Correspondents say such violence is rare in Canada, particularly on the east coast.
According to the Royal Canadian Mounted Police's Honour Roll, the last incidence of officers being shot dead on duty in New Brunswick was in 1978.
In 2005, four RCMP officers were shot dead in the western province of Alberta in the deadliest attack on Canadian police in 120 years.
They had been investigating a farm when a man opened fire. He was later killed.