The alleged plot, to spray a busy Halifax mall with gunfire, appeared to be motivated not by culture or ideology but by a small group's desire to carry out a heinous crime, according to Canadian investigators.
Lindsay Kantha Souvannarath, 23, of Geneva, Illinois, and Randall Steven Shepherd, a 20-year-old from Halifax, were arrested early Friday, authorities said. They have been charged with conspiracy to commit murder.
"This group has been stopped and Halifax is a safe place," said Brian Brennan, Nova Scotia Royal Canadian Mounted Police commanding officer.
Police in Illinois executed a search warrant at Souvannarath's Geneva home and multiple unspecified items were taken, authorities in the United States said Saturday.
Authorities received a tip Thursday morning that Souvannarath and a 19-year-old Timberlea, Nova Scotia, man planned to go to a public location in Halifax with "a goal of opening fire to kill citizens, and then themselves," Brennan said.
The 19-year-old suspect was found dead in a home, where three rifles were recovered, Brennan said. The dead man was not identified.
Another person -- a 17-year-old described as a person of interest -- was released because of a lack of evidence, Brennan said.
"All indications that we're getting from police is that this was not motivated ... by anything related to terrorism," Canadian Justice Minister Peter MacKay told reporters.
Souvannarath and Shepherd were arrested at about 2 a.m. Friday at Halifax Stanfield International Airport, Brennan said.
The four people were described as friends, and Jean-Michel Blais, chief of the Halifax Regional Police, said the alleged plot had "nothing to to with ethnic or political considerations."
The two suspects will appear in court on Tuesday.