Police spokesman Scott Pattison said they continue to look for the shooter or shooters.
Pattison said no University of Alberta students were involved. The university was quickly put on lockdown, but that was later lifted.
G4S Cash Services spokeswoman Robin Steinberg confirmed the victims were employees of the global security company. She did not have further details.
Steinberg said they've never had a fatality in Canada before.
“It's horrible to lose this many,” she said.
Such shootings are rare in Canada, where residents are nervous about anything that might indicate they are moving closer to their U.S. counterparts. 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. A shooting at an Edmonton club in 2006 left three dead.
Friday's shooting happened shortly after midnight in the Hub Mall area, which has student residences and shops. It's the university's summer session, so fewer students are living on campus.
Ian Breitzke, a student, said he was watching TV when he heard a man crying out in pain. He said when police came about 10 minutes later they broke down the door to a room behind an ATM machine and pulled out two people who looked dead.
The student said police then pulled out a man who was alive.
“The university is saddened about those who lost their lives last night and we extend our condolences to their loved ones,” the university said on its website.
It said the rest of the campus was operating as normal.