Four RCMP officers were shot and killed after conducting a raid on a marijuana grow operation northwest of Edmonton on Thursday.

It's the single deadliest incident for Canada's national police force in 120 years.

"It is with profound sadness that I confirm that four members of the Royal Canadian Mounted Police were killed today in service to our country," said RCMP Commissioner Giuliano Zaccardelli at an 8 p.m. ET news conference in Ottawa.

"It is an unprecedented and unspeakable loss."

At approximately 10 a.m. MT, a shootout broke out between police and a male suspect at a farmhouse in Rochfort Bridge near the community of Mayerthorpe, about 130 kilometres northwest of Edmonton.

RCMP spokesman Cpl. Wayne Oakes said the four officers were at a Quonset shed on the farm when they were shot by the suspect, whose body was also found in the shed.

The lone gunman then took his own life after shooting the officers.

Oakes said emergency responders went into the shed and found the dead officers.

Gunman a 'walking time bomb'

Police would not confirm the identity of the suspect, but CTV's Edmonton affiliate, CFRN, spoke with a man who identified himself as the gunman's father.

Bill Roszko said his son, Jim, was the shooter. He added Jim had an angry streak as far back as he can remember: "Because of the drugs, you know, and the bad company with bad boys . . . dragged him off the good tracks," he told CFRN.

"I don't want to have him as my son for what he was like, and the way things ended up. He is not my son."

CFRN reports Jim Roszko was the youngest in a large family, and that his troubled life led others in the family to stay away from him.

Reporting from the scene Thursday night, CTV's Sarah Galashan said others in the town described Roszko as a "walking time bomb."

Devastating loss

At a news conference in Mayerthorpe, RCMP Assistant Commissioner Bill Sweeney said: "As you can well imagine, the loss of four police officers is unprecedented in recent history in Canada. . . . It's devastating."

He added that not since the Northwest Rebellion of 1885 have so many police officers been killed in the line of duty.

The RCMP has not released the names of the deceased officers, as they are still in the process of notifying next of kin.

Sweeney said three of the officers were based in Mayerthorpe, and one was from Whitecourt, Alberta. They were all junior members of the force.

In a statement, Prime Minister Paul Martin said:

"On behalf of the Government of Canada, I would like to express my condolences to the families of the officers who were killed as they carried out their duty in enforcing the law and protecting the public.

"At this moment of difficulty and loss, you are in our thoughts and prayers."

Martin was kept informed of the developing events during phone conversations Thursday with Zaccardelli.

Alberta Solicitor General Harvey Cenaiko said he and Sweeney were to meet with the families of the dead.

"This issue was senseless in the fact that four officers were killed with regard to a grow operation," he said. "(It) goes to the seriousness of the fact that organized crime, illegal cultivation of marijuana or the illegal production of crystal meth is all around us in the province.''

Grow-ops a society 'plague'

Public Safety Minister Anne McLellan held a news conference to say she will consider tougher penalties for grow operations in the proposed marijuana decriminalization bill.

McLellan said she and Justice Minister Irwin Cotler will "want to take a look at whether we have the right resources being used in the right ways and whether we have the right laws'' to deal with illegal grow-ops, which she called a fast-spreading "scourge."

Zaccardelli called grow-ops major threats to society, and serious threats to men and women on the front line.

"This is really a plague in our society. This isn't happening in just small communities, it's happening across the country."

Reintroduced in November, the marijuana bill proposes that growers caught with more than three plants face up to five years in jail, or 18 months plus a $25,000 fine.

Anybody with more than 25 plants could face 10 years in jail, while the bill provides a maximum sentence of up to 14 years for operations with more than 50 plants.

McLellan would not answer a question about whether minimum sentences are needed to deter growers. She said, however, that police need more help.

"There is a resource issue. But I think there's also an issue around, do we have the right laws in place? Have we given the RCMP and other forces the right tools they need to deal with what is an amazing growth, quite truthfully, in these operations.''

Farm was under surveillance

Oakes said the operation began Wednesday afternoon, when officers from the local Mayerthorpe detachment placed the farmyard under surveillance.

Two officers remained at the farm overnight, and they were joined by backup Thursday morning.

The occupant of the farm had not been there overnight, but at some point he had returned.

Officers remaining on the road heard gunshots and took cover, and at least one of them returned fire. After the shots died down, none of the police on the property responded to their radios.

Emergency response teams from Calgary and Edmonton were called to the scene. The Edmonton Police Service's helicopter was called, as were three armoured vehicles from the Canadian Forces' Edmonton Garrison.

Finally, at about 2:20 p.m., an RCMP team burst into the Quonset to find the four dead officers.

Sgt. Rick Oncescu of the Calgary RCMP said two SWAT teams were called into the area, and Mounties from surrounding jurisdictions also went to the scene.

The military received a request just after 12:30 p.m. from the RCMP for assistance, said spokesman for Edmonton Garrison Maj. Scott Lundy.

Two armoured personnel carriers, an ambulance and about 20 military personnel were dispatched from the military base, but about two hours later, police told the military their help was no longer needed.

Alberta Premier Ralph Klein said he was saddened "beyond words" that such a tragedy would occur in the quiet farming community.

"Maybe it says something about how the criminal mind is changing . . . to move from big cities so perhaps they won't be noticed as much as they would in a larger centre,'' he said.

Threat assessment

Officials faced questions Thursday about whether the junior officers had adequate supervision during the exercise.

When asked during the Ottawa news conference whether a proper threat assessment was made before the officers conducted the raid, Zaccardelli replied that all proper procedures were followed and authorities had gathered enough intelligence to conduct the exercise.

"But policing in these types of major operations are never without risk," he said, " . . . and sometimes that risk is fatal."

Galashan said the RCMP "bristled" at questions regarding whether the officers had adequate supervision.

"But certainly it's a question that's going to come up in the coming days," she said.

With files from CTV's Sarah Galashan and the Canadian Press