Homicide detectives from Edmonton are now speaking with Travis Baumgartner, the security guard accused of killing three of his co-workers and wounding another in an armoured-car robbery on Friday.

A team of eight investigators from the Edmonton police service flew in to Langley, B.C. Saturday night after Baumgartner was stopped by U.S. border security at a crossing outside of Abbotsford, B.C.

"This is the best outcome we could have hoped for," said Edmonton Police Supt. Bob Hassel Sunday afternoon.

Hassel says the suspect was detained by US security until RCMP could arrive and arrest him.

Body armour, gun still missing

Baumgartner arrived at the border crossing in the same blue Ford F-150, with his mother’s licence plate on the back, that police had been searching for since he became a suspect.

The licence plate was scanned by an automated system at the crossing and set off an alarm warning security that the driver was considered armed-and-dangerous.

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Travis Baumgartner, 21, was detained by U.S. border security at a crossing near Abbotsford, B.C. Saturday night. (CBC News) (CBC )

"Sometimes you have to scratch your head and wonder why people would knowingly come up and make contact with law enforcement," said Tom Schreiber, chief border officer at the crossing.

"Maybe he thought he would be able to get through — I don't know."

Forensic investigators are now going through the truck.

Baumgartner was found with over $330,000 cash in his vehicle. Police say his company-owned gun and body armour were not recovered.

Wounded guard still critical

The three guards killed were Michelle Shegelski, 26, Eddie Rejano, 39, and Brian Ilesic, 35.

The fourth victim, Matthew Schuman, remains in critical condition in hospital, police say.  Schuman is a corporal in the Royal Canadian Air Force stationed as a firefighter at Canadian Forces Base Edmonton, who also held a second job at G4S Security.