The shooting temporarily closed the Peace Arch crossing on the U.S.-Canada border. Drivers were diverted to other crossings.
The female Canada Border Services Agency officer was shot in the neck and suffered serious injuries, Royal Canadian Mounted Police Cpl. Bert Paquet told reporters. She was breathing and conscious when she was flown to a hospital, but he had no further details on her condition.
The officer was in her booth when she was shot. Investigators were trying to figure out what happened and why, Paquet said. They hadn't confirmed whether the suspect was the van's owner.
Police were confident the unidentified man took his own life, based on initial investigations at the scene, Paquet said, adding that investigators were reviewing video and talking to witnesses. He said "at this time" there were no other suspects.
"Officers will be working 'round the clock," he said.
The man was attempting to cross into Canada from the United States, police said. The officer's identity and other personal details were withheld pending notification of relatives, Paquet said.
The Peace Arch crossing in Blaine is the third busiest port of entry on the northern border. Last month, it averaged 9,000 U.S.-bound cars a day, according to U.S. Customs and Border Protection.
The crossing features a park with a 67-foot-high monument in the form of an arch that connects the U.S. and Canada.
Canadian Brian White told reporters at the scene he was waiting to cross northward when he heard a shot.
He said guards immediately responded, and there were people screaming. Officials questioned everyone waiting to cross and took their car registration information.
Kevin McAllister, assistant general manager at the Peace Portal Golf Course, which is adjacent to the border crossing, said an employee and several guests told him 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.
U.S. authorities were notified, Paquet said.
"This is a very serious incident that occurred right on the border line," he said. "We are sharing information with them."
Washington Gov. Chris Gregoire said she spoke to British Columbia Premier Christy Clark and pledged the state's cooperation and help in 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," Gregoire said.
"This is a profound reminder of the risks that border services officers assume every day," Luc Portelance, president of the Canada Border Services Agency, said in a statement from Ottawa. "I know that the courage and dedication of our officers are second to none."
Canadian border officials will determine when the crossing will reopen, Washington state Department of Transportation spokeswoman Kris Olsen said.
"We're telling people they obviously need to use other routes to get across the border," she said.
Crossings on State Route 543 and State Route 9 remained open.
Live WSDOT camera of Peace Arch