Edmonton police say an employee of G4S Security faces three counts of first-degree murder and one count of attempted murder in connection with a deadly robbery in which three of his fellow guards were killed and another wounded early Friday morning at the University of Alberta.

At a news conference on Friday evening, Edmonton Police Supt. Bob Hassel read a statement from Sandy Baumgartner, the mother of suspect Travis Brandon Baumgartner, begging her son to turn himself in.

"Trav, I'm sorry that we had an argument last night and had bad words between us," she said. "But I want you to come home and do the right thing. Let's work this out together.

"As your mother I promise to be there by your side to support you. You're not alone Trav. Please. I love you and I want to help you. Call police now and end this peacefully."

Police also believe Baumgartner, 21, has a different Alberta licence plate number on the dark blue Ford F-150 he is thought to be driving. The new number is CAA 636. Canada-wide warrants have been issued for his arrest.

Baumgartner was one of five G4S guards making a delivery to a bank ATM on the university campus. Earlier identified as a person of interest, he was announced as a suspect on Friday afternoon.

"With the approval of the Crown, we now believe that we have reasonable and probable grounds that this is the person who is responsible for this horrific and terrible crime," Hassel said.

Michelle Shegelski was named as one of the employees of G4S who was slain early Friday at the University of Alberta. (Facebook)

Police are describing Baumgartner as "armed and dangerous" and urged anyone who encounters him to use extreme caution and contact them immediately.

Edmonton Police Service Chief Rod Knecht said earlier Friday that the killings can "only be described as a horrific act of violence."

CBC News has confirmed that Brian Ilesic, 35, Michelle Shegelski, 26, and Eddie Rejano, 39, were the three guards who were killed. Injured guard Matthew Schuman remains in hospital.

Shegelski's mother-in-law, Henrietta Shegelski, said Michelle just married her son in April.

"She was really Victor's soulmate. He was so in love with her," Shegelski said. "He's devastated. She was just such a beautiful person. So friendly. So alive. So full of fun. Everybody that knew her loved her."

Brian Ilesic, 35, had been working at G4S for a few months. He is shown here with his 12-year-old daughter in a picture sent by his family. (Courtesy of the Ilesic family)

The couple met three years ago when Victor was working for G4S after serving in Afghanistan. He left the company to go back to school.

"They loved hiking and going outdoors together and rock climbing … just did everything together," Shegelski said. "They were just so well-suited for each other."

Ilesic, 35, had only been working for G4S for several months, his brother Keith told CBC News. The family expressed their grief in a written statement sent Friday night.

"We are deeply saddened and shocked by today's events and are trying to deal with it as best we can. Our hearts go out to the other families that have also been affected," the statement said.

"Brian was deeply loved by his family and friends and leaves behind a 12-year-old daughter. We feel very blessed that he was in our lives, although taken from us much too soon.

"Brian was always a joy to be around. He will be missed dearly and will forever be in our prayers. Brian had many hopes and dreams ... due to today's tragedy his hopes and dreams are no longer possible. We ask God to take care of him now."

This picture of the scene, taken by a student in one of the residences, shows the north side of HUB Mall where the shootings took place. (Facebook)

Robin Steinberg, a spokesperson for the security company, told CBC News: "Our hearts go out to our victims' families and to all our employees at the Edmonton branch. It is just devastating .… This is the most difficult thing our company has ever had to deal with."

Steinberg said the employees who were killed would have been armed while on the job.

Police placed a roadblock around Baumgartner's home in Sherwood Park, east of Edmonton, Friday afternoon. Members of the RCMP emergency response team could be seen coming from the street where he lives.

Police located a G4S armoured van, abandoned and empty, about 70 blocks east of the university, and less than 200 metres away from the company's Edmonton property. It wasn't immediately clear whether it was related to the shooting, but officers were treating it as a crime scene.

Knecht said the Canada Border Services Agency and U.S. border security are also involved in the search.

Shots heard after midnight

The shooting took place after midnight MT inside HUB Mall, which contains retail stores and restaurants on the first floor and several storeys of student residences.

The north end of the mall, where the shooting took place, has at least four automated teller machines in a small area.

Student Ravedh Seeberath told CBC News that he heard shots around 12:30 a.m. MT while studying in the mall.

"As I was walking down, that's when about 30 tactical officers were rushing toward me, passing me with complete firearms … the whole works, and police dogs," he said.

"That's when I went back to my books, grabbed what I could, and told the other ladies in that little study area that we should get out of there."

'Busting down the door'

The bodies were reportedly found by volunteers from Safewalk, an organization that provides escorts to students on campus at night.

The volunteers apparently investigated after hearing a thud to find a wounded man behind a locked door beside a bank of ATMs in the mall. They then contacted campus security.

Ian Breitzke, 21, watched from his window as police arrived at the scene.

"They end up busting down the door and ended up pulling out all the bodies that were in there. They pulled out a couple that I could see were dead," he said.

"A few moments after that they pulled out the man who was still alive … EMS ended up taking him to hospital."

Suspect took security course in Calgary

Baumgartner has been living with his mother in Sherwood Park.

Their landlord told CBC News that his tenant took a security course in Calgary to become a guard and apparently passed his psychological exam with flying colours.

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He recently started working for G4S.

In his profile on the Plenty of Fish dating website, Baumgartner calls himself "an occasional smoker with athletic body type" and a gentleman who would make a date "feel like a princess."

"My ahmbitions [sic] in this world of ours is to better our world," he writes.

"I intend to become a CEO of a major corporation and use my power to help everyone I can. I am a people person I love talking, I'm easy to get to know and I'm very laid back."

Billy Gascoigne says he went to school with Baumgartner.

"He was a little bit of a weird guy in high school. He had some weird friends but we were all — you know, it's high school, right? We all have our own cliques and our own groups," he said.

"You know I saw him actually a few weeks ago. He was with his mom. He said he was doing well. He said he got the job at G4S."

Gascoigne said Baumgartner was into video games and had good marks in school.

University offers help

A university administration statement released Friday said the school is "saddened about those who lost their lives last night, and we extend our condolences to their loved ones."

"The safety and security of our students and staff is our first priority, and our campus protective services are working closely with Edmonton police," the statement said.

"Counsellors are available to students living in the residential portion of HUB. If there are students directly affected by this tragic incident who feel they cannot take exams scheduled for Friday, they can defer those exams per our existing procedures."

Students who live in the Hub Mall residences were allowed to return to their homes Friday night.

The university announced via Twitter around 9:45 p.m. MT that the rest of HUB Mall would remain closed until further notice.

Other parts of the campus were operating normally.