"It's a vast warehouse complex and we found victims throughout the complex," said acting Insp. Malcolm Allan. "We have dozens of witnesses. This individual went throughout the business assaulting people."
When workers at the Loblaws distribution centre in northwest Edmonton were finally allowed to leave, many were visibly shaken.
"His car was parked right beside mine," one man said of his encounter with the assailant. "He said, `you want to get stabbed?' "
The man paused, his voice began to crack and then he drove away, telling reporters: "Sorry, guys, can't take it, gotta go."
Aaron Nganatafam, who had been inside the warehouse, said he knew the attacker and considered him "very weird. No friends, nothing ... It was like in the movies, really."
A suspect, 29-year-old Jayme Pasieka, was arrested without incident on the city's south side about three hours later after officers received a tip from "a vigilant citizen" who noticed a vehicle matching a description that had been issued by police.
Allan said Pasieka is an employee at the warehouse, which employs at least 100 people and handles food for the Superstore grocery chain, though it is not known if he was on shift Friday.
Pasieka was convicted in 2010 of assault with a weapon and uttering threats and was sentenced to 15 months probation.
The Edmonton Journal covered the trial and said Pasieka threw eggs at a neighbour's vehicle, set a heart-shaped fire on their street and brandished a bow and arrow. Pasieka told police he did it in the name of The Queen. The man's father told court he had suffered a head injury three years earlier.
Allan said police now have to sort through a complex crime scene that spans an area about the size of two football fields.
He said a motive for the attack isn't yet known but noted the assailant was armed and appeared to be wearing some sort of body armour: "That suggests there may have been some pre-planning."
A Loblaw spokesman said the company's full attention "is on the health and well-being of our colleagues."
Kevin Groh, vice-president of corporate affairs, would not comment further "given this is an active police investigation."
The identities of the victims have not yet been released, but police said two of the survivors were quite seriously injured while the other two sustained non-life-threatening injuries.
"It was quite chaotic at first," said Allan. "There's a lot of traumatized people. We have our victims' services people in a full-court press in that regard. We're trying to help these individuals as best we can."
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