Two people have been charged with conspiracy to commit murder in connection with an alleged plot to attack a Halifax mall.

Nova Scotia RCMP announced Saturday they have laid charges against 23-year-old Lindsay Kantha Souvannarath, of Geneva, Ill., and 20-year-old Randall Steven Shepherd, of Halifax.

A third person -- a 17-year-old male from Cole Harbour, N.S. -- was released without charge overnight, but police say he remains under investigation.

Police arrested three people after acting on a Crime Stoppers tip received earlier in the week.

A fourth suspect, a 19-year-old man, was found dead by police at his parents' home in Timberlea, N.S., just after 1 a.m. on Friday.

Speaking to reporters Saturday, police said they seized three long-barrel guns from the Timberlea home.

Police allege the suspects planned to use the guns to achieve their goal of "opening fire to kill citizens, and then themselves" on Valentine's Day at the Halifax Shopping Centre. The mall advertises itself as the largest shopping centre in Nova Scotia.

"This is a reminder that this type of incident can happen anywhere," Halifax Police Chief Jean-Michel Blais said in a statement. "Recognizing our citizens may be anxious in the wake of this news, we have additional high visibility patrols in and around the city. We encourage people to go about their daily lives."

Nova Scotia RCMP Asst. Commissioner Brian Brennan described the suspects as "four individuals that had a friendship."

He added: "Their friendship is not based on culture or ideology. They are four individuals who formed a friendship and decided to plan and commit a heinous crime."

Police would not comment on a possible motive, but said the individuals seem to have communicated online.

Brennan said a 20-year-old man and 23-year-old woman were arrested at the Halifax Stanfield International Airport around 2 a.m. on Friday. He said the woman was arriving by plane and the man was there to meet her.

The Geneva Police Department said Saturday they executed a search warrant at the home of the 23-year-old woman at the request of Canadian police. Multiple items were taken from the residence, but police did not provide any further details.

Geneva police said the woman was not known to authorities, and her family is co-operating with the investigation.

The two suspects are expected in court Tuesday morning.

Brennan did not comment on the circumstances surrounding the 19-year-old's death in Timberlea. He said Nova Scotia's Serious Incident Response Team is currently investigating.

One of the man's neighbours said the 19-year-old didn’t interact with others in the community.

"He was one of those people who kept to himself, not a people person," Steven Greenwood, 19, told The Canadian Press.

Greenwood's mother, Cindy, awoke early Friday morning to sight of armed police officers outside her home.

"I just found out this morning what the plan was … that's scary," she said.

"It's a little scary to know this is just the next house down," she added.

The 50-year-old knew there was a couple living in the home, but didn't recall meeting their son.

Another resident told The Canadian Press that 19-year-old who had died had attended a nearby school, and that the family had lived in area for many years.

Greenwood said she felt sorry for the man's family. A man in house asked reporters to leave on Saturday, saying he had just lost his son.

Earlier Saturday, Justice Minister Peter MacKay said the alleged plot would have been "devastating," but was not linked to terrorism.

"What I can tell you is that this appeared to be a group of murderous misfits that were coming here, or were living here, and prepared to wreak havoc and mayhem on our community," he told a news conference.

"Make no mistake about it, there could have been a real tragedy and it would have marked our city and our province forever."