A group of "murderous misfits" planned a massacre on Valentine's Day in Atlantic Canada's largest regional shopping mall but the alleged plot was foiled by police after an anonymous tipoff, the justice minister said on Saturday.
Police charged two people with conspiracy to commit murder and released a third suspect in the alleged plot to shoot as many people as possible in the Halifax Shopping Centre. A fourth man linked to the plot was found dead in a house in Halifax, police said.
"Based on what we know so far, it would have been devastating, mass casualties would have been a real possibility," Justice Minister Peter MacKay told reporters.
"The attack does not appear to have been culturally motivated, therefore not linked to terrorism," he said.
In a sign of heightened tensions, streets around the mall were closed on Saturday evening as police blocked the entrances after reports of an active shooter.
That incident was related to "kids with slingshots" and seven youths were in custody, police said.
MacKay said a 19-year-old Canadian man and a 23-year-old American woman, believed to have been in contact online, allegedly planned a shooting at a public venue.
Police said on Friday they obtained information that suggested the two had access to firearms and intended to kill people, and then themselves.
"This appeared to be a group of murderous misfits that were coming here, or living here, and were planning to wreak havoc and mayhem on our community," MacKay said on Saturday.
"To be clear, all suspects are either dead or in custody," he said.
Police said Lindsay Kantha Souvannarath, 23, and Randall Steven Shepherd, 20, are due to appear in court on Tuesday.
The two were arrested at Halifax airport after Souvannarath arrived from Illinois and was met by Shepherd, said police, who are investigating the death of the 19-year-old man.
"There were three long-barrelled rifles seized during the investigation and all three were seized at the residence...where the 19-year-old was found deceased," Nova Scotia RCMP Commanding Officer Brian Brennan told reporters.
Canadian media identified him as James Gamble and several reported he had shot himself. Police declined to confirm those details.
CBC News said a blog linked to Gamble featured "dark images of death, shootings" as well as security footage from the 1999 Columbine high school massacre in Colorado.
On Friday, Brennan said the alleged attackers were "a group of individuals that had some beliefs and were willing to carry out violent acts against citizens".
Extra security measures have been taken at the shopping mall, police said. The plot was foiled after "a single Crimestoppers tip...that originated in Canada," Brennan said.