The man who unleashed bullets on a busy Danforth stretch Sunday night was suffering from “severe mental health challenges” and struggling with psychosis and depression, his devastated family said Monday.

Just after 10 p.m. Sunday, a lone gunman dressed in dark clothing and a black baseball cap fired upon groups of people as they were enjoying a warm summer night out in Toronto’s Greektown neighbourhood — killing a 10-year-old girl and an 18-year-old woman, and injuring 13 others.

The gunman, identified Monday as Faisal Hussain, 29, then died of a self-inflicted gunshot wound, according to police sources.

“We are at a terrible loss for words but we must speak out to express our deepest condolences to the families who are now suffering on account of our son’s horrific actions,” Hussain’s family wrote in a statement Monday.

“We are utterly devastated by the incomprehensible news that our son was responsible for the senseless violence and loss of life that took place on the Danforth.”

Twin investigations are now underway to determine key details in a shooting that has left the city grieving, shocking the residents in the vibrant Greektown neighbourhood where police descended Monday to collect evidence and photograph bullet casings.

Chief among the questions now are what motivated the gunman, and how he got a hold of a handgun — particularly in light of his family’s claims he suffered from psychosis. The family’s statement said the interventions of professionals were unsuccessful in helping him, and medications and therapy “were unable to treat him.”

“While we did our best to seek help for him throughout his life of struggle and pain, we could never imagine that this would be his devastating and destructive end,” the statement read.

Toronto police Chief Mark Saunders said at a news conference at police headquarters that the investigation was “very fluid, it is very new.”

“We do not know why this has happened yet,” he said. “It’s going to take some time.”

While Toronto police are probing the actions of the shooter, Ontario’s police watchdog, the Special Investigations Unit (SIU), is examining Hussain’s death. Officials with the SIU confirmed Hussain died following an exchange of gunfire with two Toronto police officers on Bowden St. He then fled the area, but was found dead on Danforth Ave.

While the SIU has not provided any details, police sources tell the Star Hussain died of a self-inflicted gunshot wound.

The two officers involved in the shootout were “visibly shaken” by the encounter, said Toronto Police Association president Mike McCormack. The alleyway where the exchange of gunfire took place remained cordoned off by yellow tape Monday, a police cruiser towed from the scene earlier in the day leaving broken glass in its wake.

Police are now digging into the suspected shooter’s background, and have gotten a warrant to search a unit in a residence on Thorncliffe Park Dr. On Monday evening, two Toronto police officers sat outside the door to a mid-level apartment unit, while a security guard watched the front entrance.

Prior to Sunday’s shooting, the Hussain family had already suffered tragedy, residents of the building said.

Khalid Malik said Hussain had a sister who died several years ago in an accident, and has a brother who has been in a coma in hospital for the last year.

Mirza Baig, a long-time resident of the building, said Hussain’s father was also sick and possibly suffering from Parkinson’s.

Malik described Hussain as a quiet man he would sometimes run into on the street. The two would shake hands and Hussain would give him a cigarette but never said much.

“Unbelievable,” Malik kept repeating Monday evening, speaking to reporters.

Of the 15 victims shot in the rampage, eight were female. The surviving thirteen victims range in age from 17 to 59 years old, and remain in hospital with injuries ranging from minor to critical.

In a news release Monday evening, Toronto police identified the killed woman as Reese Fallon, 18, who lived in Toronto’s Beach neighbourhood. A spokesperson for the devastated family said the family had requested privacy, adding he personally knew her to be as caring and “whip smart.”

Fallon’s younger sister posted a lengthy tribute on Instagram Monday evening. “Today has been the hardest because I haven’t just lost a sister I’ve lost my lifelong best-friend and anyone who knew us knew that when we were together we were inseparable,” she wrote.

“I am crushed and broken and there won’t be one minute that goes by for the rest of my life that I won’t think of you.”

Police did not identify the 10-year-old girl who was killed, saying her family did not want her name released.

Witness Ali Demircan, who was sitting with friends on a bench near Logan and Danforth Aves. Sunday night, told the Star he saw an injured woman during a break in the shooting.

Demircan said the woman, who was holding her arm where she appeared to have been shot, approached him and asked him to call 911, but the shooting started again before he could do so.

“When I turned back there she was lying behind a small tree on Logan avenue. People were trying to help her and do CPR,” Demircan said.

“It was terrible.”

Neither police nor the SIU would speculate on a motive for the shooting.

“He received a gunshot wound, but I’m not going to expand on that,” Toronto police Chief Mark Saunders said at the Monday news conference.

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After Hussain was identified, the National Council of Canadian Muslims released a statement condemning the shooting attack.

“Like all Canadians, we grieve the loss of our fellow community members and our thoughts and prayers are with the survivors, the families and friends of the victims, and all Torontonians during this absolutely heartbreaking time,” NCCM Executive Director Ihsaan Gardee said in the statement.

The gunman was randomly shooting like someone “in a video game,” witness Lenny Graf told the Star.

“He was very relaxed, it was pretty disturbing,” said Graf, who was with his family having dinner at Christina’s Restaurant when his kids asked to go play at the fountain in the Alexander the Great parkette on Logan Ave.

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When Graf got outside, he heard loud popping sounds.

“I thought it was firecrackers, except that people started to run away, and crouch down and scream,” he said.

The gunman, who was dressed in all black, was on the sidewalk on the north side of Danforth, near the fountain, Graf said.

“I saw him finish shooting some people and then walk away,” Graf said.

Graf said he remembers seeing someone on the ground, then seeing paramedics and police arrive.

“I always thought if I was up against a guy shooting people, I would run up and grab the gun or something, but there was no way to do that,” he said.

Androo Leipurts was bartending at Brass Taps pub when he heard a loud commotion and looked out the window to see people running. He saw a woman running, then fall to the ground.

“I essentially saw someone’s daughter drop to the ground and roll,” he said.

Mayor John Tory, who headed to the shooting scene Sunday night, offered his condolences to families of the victims and urged residents not to jump to conclusions about what transpired and why.

In a statement, Tory called the shooting a “despicable act.”

“On behalf of all Toronto residents, I am outraged that someone has unleashed such a terrible attack on our city and people innocently enjoying a Sunday evening,” Tory said.

“ ... While our city will always be resilient in the face of such attacks, it does not mean such a cowardly act committed against our residents is any less painful — this is an attack against innocent families and our entire city.”

Danforth Ave. was closed between Broadview and Pape Aves. until shortly after 5:30 p.m.

The normally vibrant strip of the Danforth was eerily quiet in the morning, hours after the shooting. There were no parents walking their children to day camp, no businesses open and no one was grabbing pastries from the local coffee shops.

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No one was allowed inside except for a few business owners escorted by police to grab belongings. All morning, residents stopped, stared, shook their heads and muttered words like “unbelievable” and “isn’t this crazy?”

At 7 p.m. Monday, people streamed into Calvary Church, just north of Danforth Ave. for a prayer vigil that was closed to media.

Some carried flowers, others hugged and fought back tears.

“We love the Danforth and were so sad this happened here,” said Nancy Kruger, who said she lived in the neighbourhood when she was younger and had returned to support local businesses.

“We are not afraid to come back here,” she said.

Shiraz Mohamed, an Imam at nearby Madinah mosque walked with a group of about 20 others from the mosque to the vigil.

“We are part of this community and we are affected like anybody else so we wanted to show our support,” he said on his way there.

Three patients were taken to Sunnybrook hospital late Sunday. Five were taken to St. Michael’s Hospital with injuries ranging from serious to critical. Three of the patients at St. Mike’s underwent “immediate, life-saving surgery.”

Michael Garron hospital, formerly the Toronto East General Hospital, treated two gunshot victims, who are in stable condition. The hospital also treated five others who were hurt, but they have since been released.

Correction: July 23, 2018 — An earlier version of this story had the wrong credit for the screen capture of a video of the shooting.

With files from Julien Gignac, Premila D’Sa, Jenna Moon, Amy Dempsey, Marco Oved, Tamar Harris and May Warren