The lone survivor of an armoured car heist in Edmonton — that left three others dead — opened his eyes and squeezed his wife's hand on Sunday night, according to sources.

CBC News has learned that Matthew Schuman, a corporal in the air force who held a second job at G4S Security, sustained head injuries during the attack at the University of Alberta's Hub Mall last week. The nature of his injuries — described as critical — have never been disclosed.

"This is best news we have had in the last sixty hours or so," one source stated.

One of Schuman's coworkers at G4S, Travis Baumgartner, faces three counts of first-degree murder and one count of attempted murder in the shooting. Michelle Shegelski, 26, Eddie Rejano, 39, and Brian Ilesic, 35 were shot and killed.

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

Baumgartner was arrested Saturday afternoon while attempting to enter the United States near Abbotsford, B.C.

He is now being held in Langley, B.C., where he is being questioned by Edmonton police investigators. Police say he is co-operating and is expected to be taken to Edmonton on Wednesday.

G4S opening its own investigation

Edmonton Police Chief Rod Knecht said at a news conference on Monday that he intends to visit each of the victims' families this week.

"None of us can truly understand the loss these families have experienced, especially in so shocking a brutal fashion," he said.

The crime scene has been a challenge for some of his officers who will require counselling in the weeks to come, Knecht said.

"Our investigators have described the scene as one of unimaginable carnage," he said.

The armoured-car company said it will be doing its own investigation into the robbery.

G4S Canada CEO Jean Tallion waits to speak at a news conference Monday. (CBC)

It has flown in its own security experts to carry out the investigation, which is standard practice in such cases, said G4S Canada CEO Jean Tallion.

"I cannot begin to describe the shock and grief that the G4S family is still feeling," he said. "We lost three valued members and another remains in critical condition in hospital and our thoughts and prayers remain with their family and friends."

Federal Occupational Health and Safety officers also confirmed Monday they have launched an investigation into the deaths as well.

'Best outcome we could have hoped for'

A team of eight investigators from the Edmonton Police Service flew in to Langley on Saturday night after Baumgartner, who worked as a security guard, was stopped by U.S. border security at a crossing outside of Abbotsford.

"This is the best outcome we could have hoped for," Edmonton police Supt. Bob Hassel said, adding that Baumgartner was held by U.S. security until RCMP were able to arrive to arrest him. He was not carrying a passport, but had more than $330,000 in cash with him in his vehicle, police said Sunday.

Baumgartner, who had only been on the job for a few months, faces three counts of first-degree murder, one count of attempted murder and four counts of robbery using a firearm.

Portraits of Shegelski, Rejano and Ilesic have started to emerge.

Brian Ilesic, 35, was among three security guards shot and killed Friday at the University of Alberta in Edmonton. (Courtesy Keith Ilesic)

Ilesic's brother, Keith, said in an email that the devoted father grew up in Edmonton and also lived in Vancouver for a short time before rediscovering religion within the past two years and becoming a regular churchgoer. He was described as an outdoorsman who loved Japanese cuisine and going to the movies.

"Brian was always the type of person to put his family and friends before himself. He was a loyal friend," Keith Ilesic wrote in an email to CBC News.

"But his greatest love was for his daughter ... who he'd do anything and everything he could to make her happy and give her a promising future."

Schuman was stationed as a firefighter at Canadian Forces Base Edmonton.

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 was identified as a suspect.

'Sometimes you have to scratch your head and wonder why people would knowingly come up and make contact with law enforcement.' —Tom Schreiber, U.S. Customs and Border Protection

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.

"Sometimes you have to scratch your head and wonder why people [wanted by police] 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."

Police said they still have not found Baumgartner's company-owned gun and body armour after examining his truck