TORONTO - In the aftermath, blood, tears, death and questions.

Calls by Toronto's mayor for a "war on gangs," for help from a visibly shaken police chief.

Bullet casings, beer bottles and the discarded remnants of a barbecue party that ended in the worst gun violence in this city's history.

Two young people died and 23 were shot - including a toddler who was grazed by a bullet. A pregnant woman was trampled in the panic as residents and guests fled an east-end public housing project.

Fourteen-year-old Shyanne Charles, of Toronto, and 23-year-old Joshua Yasay, of Ajax, were pronounced dead at the scene following a blazing gun battle.

Toronto Police Chief Bill Blair blamed the violence on a gang-related dispute.

"This altercation involved two individuals and as a result, there was an exchange of gunfire," Blair said.

"There is strong indication that there may have been a gang involvement," he said, suggesting the individuals police are seeking "are associated with gangs."

The shooting spree erupted following an altercation around 10:42 p.m. at the party Monday, which was attended by up to 100 people.

The oldest surviving victim was 33, Blair told reporters earlier, calling most of the injured "innocents."

He said the "horrendous" shooting, which immediately became the focus of an intense police investigation, is "shocking to the entire community."

At the cordoned-off street where police were conducting door-to-door interviews with residents, an obviously-shaken Blair told reporters "this is the most serious crime of its kind that has ever taken place in the City of Toronto.

"I think every citizen in Toronto will be a little shaken up by what has transpired here," he said early Tuesday morning, shortly after cruisers from all over the city rushed into the area.

Residents were already expressing fears in the wake of recent shootings, including one on June 2 where two people were shot at the Eaton Centre.

Burgers, hot dogs and jerk chicken was cooked for the annual neighborhood event at a host townhouse, which was the mainstay for children the party was initially held for.

But QMI Agency learned that as adults from all over the city began arriving in response to Twitter postings about the barbecue, ganja and Caribbean rum became readily available.

Calling the hell that was unleashed "the scariest thing that has happened here," a young resident said a man appeared to have become upset when people rejected him.

"I heard the guy wasn't accepted," she said. "He said, ‘I'm going to get my guys, so you'd better be ready.'"

The resident, who did not want to be named, said, "He came back with one or two other people and started shooting."

A total of 16 ambulances, some from surrounding regions, and the Toronto EMS bus responded to the scene and rounded up victims. Two who sought their own medical attention later contacted police.

"This is unique," Toronto EMS Deputy Chief Garrie Wright said of mayhem medics faced. "But our paramedics are highly trained. They train for incidents just like this."

A handgun was seized by police, but its calibre and type was not disclosed.

-- With files from Jenny Yuen