Travis Baumgartner was stopped Saturday near a border crossing in Lynden, Washington, southwest of Abbotsford, British Columbia.
He was driving a Ford F-150 truck with the Alberta license plate that police had been seeking, Police Supt. Bob Hassel said at a news conference. Hassel said the suspect tried to get through the border with his driver's license. He had the cash in a backpack.
Thomas Schreiber of U.S. Customs and Border Protection said the suspect didn't have a gun and was arrested without incident.
Baumgartner, 21, had been on the run since Friday when four armed guards were gunned down, three of them fatally. He faces three counts of first-degree murder and one count of attempted murder.
Hassel said the injured guard remains in critical condition.
Baumgartner was the fifth member of a G4S Cash Solutions crew that was re-loading bank machines at a University of Alberta mall and residence where the shooting happened, police said. The armored truck was found abandoned but running not far from the security company's offices. Dead at the scene were Michelle Shegelski, 26; Eddie Rejano, 39; and Brian Ilesic, 35.
Police had launched an international manhunt to find Baumgartner. Hassel said Baumgartner is currently being held at a police detachment in Langley, British Columbia, and is expected to be transferred back to Edmonton sometime in the next week.
G4S Cash Solutions spokeswoman Robin Steinberg said the company would conduct its own investigation into the shooting. Baumgartner had only been on the job for three months.
"We applaud the dedication of the Edmonton Police Service, and other law enforcement agencies in apprehending Travis Baumgartner today," Steinberg said in a statement. "Our thoughts remain with the families and friends of the victims and also with the Baumgartner family."
Baumgartner's mother issued a statement Friday pleading for her son to surrender and apologizing for an argument they had.
Such shootings are rare in Canada, where residents are nervous about anything that might indicate they are moving closer to U.S. levels of gun violence. The oil boom town of Fort McMurray, Alberta, however, often has drug-related shootings, and Vancouver often has gang shootings. Gunfire at Toronto's most prominent mall this month left two dead and several injured and a shooting at an Edmonton club in 2006 left three dead.
Steven Munz, a close friend of Baumgartner, had said that Baumgartner had been on the job for only three months and wanted to eventually become a police officer, but said Baumgartner didn't believe he had what it took. Munz said he had noticed a change in his personality in the last year, and that he had been irrational at times.
In a profile on the dating website Plenty of Fish, Baumgartner bills himself as an armored car guard interested in video gaming. A photo shows him shirtless holding a cell phone. He says he has a laid back personality and a "10" physique.
"I'm a great guy. We don't come around often," he writes.
But his Facebook page is much darker, quoting the character of the anarchist Joker from the movie "Dark Knight" and musing about "popping people off."
Baumgartner lived with his mother and step-sister in Sherwood Park, a bedroom community just east of Edmonton.
(Copyright 2012 by The Associated Press. All Rights Reserved.)