The suspected shooter behind a deadly attack that took place on the Danforth this weekend was buried Wednesday morning after dying of a self-inflicted gunshot wound, a source close to the family told CTV News.

A firearm was recovered after an 18-year-old woman and a 10-year-old girl were fatally shot on Danforth Avenue on Sunday at around 10 p.m.

Faisal Hussain, who police say carried out the shooting, was pronounced dead at the scene. The Special Investigations Unit has not confirmed if the suspect was shot by police or if his injuries were self-inflicted.

The firearm used in the deadly attack originated from the United States, sources tell CP24, and the weapon was stolen during a break-and-enter in Saskatoon a few years ago, according to CTV News Toronto.

A police source tells CTV News Toronto that the theft of the gun in Saskatoon occurred around the same time that Hussain’s brother, Fahad, was arrested in the city on drug charges.

Hussain’s brother was also connected to the seizure of more than 30 guns in Pickering last year, according to the same source.

When Hussain’s Thorncliffe Park Drive apartment was searched this week, sources said, police found ammunition and large capacity magazines.

Investigators are working with officials in the U.S. to determine how the gun used in the shooting spree ended up in Canada, according to sources who spoke to CP24.

Investigators believe the weapon used in the shooting was obtained illegally from a “gang-related” source in the city and that the gunman did not have a licence to possess the gun used in the attack, sources also told CP24.

Police have not confirmed a motive for the shooting, but in a statement released on Monday, Hussain’s family said that he struggled with “severe mental health challenges” and “psychosis.”

According to a former classmate and friend who spoke with CTV News Toronto, Hussain’s behavior was concerning, even in high school.

“He’d walk around with a sketchbook and he would just write things in there. And we took a class together, I believe it was philosophy class, and I just remember that in class I would see him writing or sketching and it was all very dark and hard for me to understand,” she said of their time together at Victoria Park Collegiate nine years ago.

The friend kept in touch with Hussain on Facebook after high school, but became concerned when he started to post pictures of guns.

“He would talk about beating up his mom,” the friend said. “I vividly remember that because I reached out to him and I said to him ‘you know, that’s super inappropriate and I really hope these are just lyrics and you are not meaning these things.’”

A teacher from the same school, who did not want to be named, told CTV News Toronto that he had to call the police after a conversation with Hussain.

According to the teacher, Hussain was asked what he wanted to do with his life. He responded by saying “I want to kill someone.”

“And I was stunned,” the teacher said. “I said, ‘Why? What did they do to you?’ And he said ‘No, I just want to kill somebody.’”

The teacher then said Hussain thought killing someone ‘would be cool.’ The teacher reported the conversation to the principal, who in turn called the police.

Hussain was investigated by police under the Mental Health Act.

On Tuesday, Federal Public Safety Minister Ralph Goodale told reporters that Hussain was not on any federal watchlists.

In a statement issued Wednesday, Goodale’s office said that there is still no known connection between the incident and national security.

“Toronto Police remain the lead and it's still early in the investigation. At this time, there is no national security nexus to the shooter,” the statement reads.

Ontario’s Minister of Community Safety and Correctional Services told reporters Wednesday that the statements made by Goodale’s office “stands.”

“There is nothing further at this point,” Michael Tibollo said. “I think there has been speculation about where the gun originated from, but we have to let the police do their work.”

Police are looking into Hussain’s past and are working to determine what may have prompted him to commit Sunday’s massacre.

As part of the overarching investigation, police are also working to determine the provenance of the semi-automatic handgun that was used in the attack.

Along with the two deaths, Sunday’s massacre left 13 others injured.

ISIS claims responsibility for shooting

ISIS has claimed responsibility for the shooting on Sunday but police in Toronto say that there is “no evidence” to support the claim.

Reuters reported on Wednesday morning that ISIS claimed responsibility for the incident in a statement released by its AMAQ news agency, which referred to the gunman as “a soldier of the Islamic State” who “carried out the attack in response to calls to target the citizens of the coalition countries.”

In a statement issued a few hours after the claim was first published, Police Chief Mark Saunders said that while officers continue to examine “every investigative avenue,” there is no evidence at this point to suggest that the gunman was inspired by ISIS.

“At this stage, we have no evidence to support these claims,” Saunders said. “Accurate information about this investigation will only be released by the Toronto Police Service. We will continue to explore every investigative avenue including interviewing those who knew Mr. Hussain, reviewing his online activity, and looking into his experiences with mental health.”

Tibollo also confirmed that, as of Wednesday afternoon, there is nothing that supports ISIS’ claim.

ISIS has made false claims in the past

It should be noted that ISIS regularly claims responsibility for attacks carried out in the West but those attacks are not always found to be inspired or directed by the terrorist organization.

ISIS claimed responsibility for the Las Vegas massacre in September through the AMAQ news agency but law enforcement officials in the U.S. have repeatedly dismissed any link between that attack and international terrorism.

Last June, ISIS also claimed responsibility after a masked gunman set a deadly fire inside the Resorts World Manila casino and hotel complex in the Philippines but law enforcement officials there have insisted that the attack was the work of a mentally ill man and was not an act of terrorism.

“They say one of our soldiers but what does that even mean,” former Ontario Provincial Police commissioner Chris Lewis told CP24 on Wednesday morning. “I am Roman Catholic so I might by a soldier of the Roman Catholic religion. It is really tough to understand. I think the main focus for us in the city and the society is that bad things happen from bad people at times. What their motivation is doesn’t take away from the fact that young people are dead and other people are hurt.”