SURREY, B.C. -- A female Canadian border guard was shot at one of the busiest crossings in Canada on Tuesday and the gunman died after apparently turning his weapon on himself, RCMP say.

The Douglas border crossing, known better as the Peace Arch crossing, was closed in both directions Tuesday night, with Sgt. Jennifer Pound of Integrated Homicide Investigation Team announcing via Twitter that the unit would be taking over the file because of the "attempt murder aspect" of the incident.

"The first report at the scene revealed that a male, a lone male, had shot an officer in her booth," said Cpl. Bert Paquet, earlier in the day.

"At the instant following the shooting of the officer, the lone male had been pronounced dead at the scene from what appeared to be a self-inflicted gunshot wound."

Paquet said the officer's condition isn't known, but she was breathing when she was loaded into an air ambulance. He said it appeared she'd been shot in the neck and her injuries were serious.

"We haven't confirmed the identity of the suspect yet. He was entering Canada in a vehicle that bore a Washington plate."

Public Safety Minister Vic Toews said in a statement he was deeply concerned at the news.

"This event is a sobering reminder of the dangerous conditions faced daily by the men and women of our law enforcement agencies as they work to protect the safety and security of Canadians."

Shirley Bond, B.C.'s minister of justice and attorney general, said the RCMP will be working with their colleagues in Washington state during the investigation.

She said Premier Christy Clark and Governor Chris Gregoire have talked about the incident, are committed to a safe and peaceful border and will work with federal officials in both countries to protect border guards.

Calling Canadian border guards "an extension of our Washington family," Gregoire pledged in a statement full co-operation during the investigation.

"This tragedy hits especially close to home and reminds us all that our public safety officers put their lives on the line every day to protect the rest of us," she said.

A spokeswoman with the Canada Border Services Agency said traffic was being diverted around the crossing.

Glen Pederson, a local resident, said he heard two gunshots in the afternoon but didn't think much of the noise.

"I thought it was these guys next door, it's a construction site. There's a house being built here, there's been all kinds of banging going on for days and weeks."

Pederson said when he heard a helicopter buzzing over his house, he went outside to his front patio and then walked over to the park at the border to see what was going on.

He said he could see a white van stopped near the first booth, closest to the customs building, and surrounded by yellow police tape. The van had Washington state licence plates, he said.

Pederson said dozens of cars were still waiting at the crossing in the late afternoon.

"There was cops there so fast it wasn't even funny," he said.

Kevin McAllister, assistant general manager at the Peace Portal Golf Course, which is adjacent to the crossing, said an employee and several guests reported to him that they heard shots fired at around 2 p.m.

"Two shots were fired," he said. "We've heard fire, police, ambulance heading southbound on (Highway) 99, which is probably about a couple hundred yards from the 18th green. So that's what they heard when all hell broke loose."

McAllister said he also heard and saw a police helicopter hovering over the 10th and 11th fairways, which are the closest fairways to the highway and the border crossing.

He said the helicopters stopped about 2:40 p.m.

"Staff are coming in, talking about it," he said.

Kelsie Carwithen, a spokeswoman with the B.C. Ambulance Service, said one air and two ground ambulances were on the scene.

She said the service was called just before 2 p.m., but couldn't provide further details.

Lisa Moeller, public affairs for the police department in Blaine, Wash., said members were helping the Washington State Patrol in closing Interstate 5 at exit 275 and diverting traffic to the nearby truck crossing.

A provincial travellers' report says Highway 99 is closed in both directions two kilometres north of the Washington border.

The Peace Arch border point is the third busiest crossing between Canada and the United States.

An average of 3,500 cars pass through the crossing on a slow day, and during peak periods about 4,800 vehicles will move through the border.

During those peak periods, border delays can reach four hours on either side of the border.