A manhunt is under way in the Canadian city of Moncton after three officers were shot dead and two wounded.
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 told the BBC the officers were shot responding to reports of an armed man wearing camouflage clothing.
That initial call was at 19:20 local time (22:20 GMT).
The two wounded Royal Canadian Mounted Police officers were taken to hospital with non-life threatening injuries, a police spokesman said.
Drivers have been asked to stay away from the area.
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.
Witnesses said they heard the first shots in north-west Moncton at about 20:00 local time (23:00 GMT). More shots were reported about two hours later.
Moncton resident Heidi James told broadcast CTV that she and her husband heard four or five shots.
She said her husband looked outside the window and saw a "shot-out" vehicle and what looked like a body covered with a blanket.
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 pointed 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.
Leblanc said he quickly returned to his home and stayed there with his family. At one point a neighbour posted on social media that their kitchen window had been shattered by gunfire.
Canadian Public Safety Minister Steven Blaney tweeted that he was "shocked by the tragedy'' and that his thoughts and prayers were with police officers.
Correspondents say such violence is rare in Canada, particularly on the east coast.
In 2005, four Royal Canadian Mounted Police 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.