TORONTO -- A man convicted of two counts of second-degree murder in a shootout at a 2012 community barbecue in Toronto was sentenced Wednesday to life in prison with no chance of parole for seven years.

Folorunso Owusu, who was 17 years old when he fired a gun sparking pandemonium on Danzig Street, was sentenced as an adult.

Two people -- 23-year-old Joshua Yasay and 14-year-old Shyanne Charles -- died in the shootout, which Toronto police called an "unprecedented" episode of violence that injured more than 20 others, including a 22-month-old child.

Yasay's family expressed relief after hearing that the person responsible for the "exceptional" young man's death had been sentenced as an adult.

His sister Jennilyn Yasay said that while they will suffer from the loss forever, she hopes her family can finally get some closure.

"It's our time for our family to heal," she said.

Afifa Charles, Shyanne's mother, said she hasn't slept properly since her daughter's death.

"To see your daughter laying on the ground dead and there's nothing you can do is the worst pain a mother, a father can ever feel," she said tearfully outside court.

Justice Ian Nordheimer said Owusu -- who was also found guilty by a jury on March 17 of one count of attempted murder, one count of aggravated assault and one count of reckless discharge of a firearm -- has not accepted responsibility for his actions.

Owusu maintained throughout the trial that he didn't fire his gun, starting a wild shootout in a crowd of 200 people that included small children.

Court heard Owusu came to the party armed with a handgun knowing members of a rival gang would be there.

When he arrived at the party in Toronto's east end, Owusu came across a man with the street name of "Gifted," who was checking attendees to see if they were welcome, Nordheimer said as he delivered his sentencing decision.

The man flashed a handgun and told Owusu to leave, court heard, before an older man told Gifted to put the gun away.

Owusu, the judge said, then took out his gun and fired at Gifted, who was struck twice. The man, as he fell to the ground, fired at least 11 shots, one of which struck Owusu.

Court heard that another man then took out a submachine gun and opened fire. It was bullets from Gifted's gun and the man with the submachine gun that killed Charles and Yasay.

Nordheimer said Owusu is responsible for their murders, even though his bullets didn't kill the two, because he was involved in a dangerous act that led to their deaths.

The judge also noted that those three guns were never found.

The judge said Owusu's lawyer argued his client's actions were impulsive and spontaneous.

Nordheimer disagreed, saying Owusu brought a loaded handgun to a street party where he knew there may be rival gang members and shot his gun knowing opposing gang members "would respond in kind."

"There is nothing impulsive about (Owusu's) actions," Nordheimer said, calling it the "antithesis of spontaneity."

Nordheimer also noted an evaluation considered Owusu at medium risk to re-offend.

The judge also said the public's interest played a role in his decision to sentence Owusu as an adult.

"Society has an interest in ensuring that young persons, who commit serious violent offences, are subject to meaningful penalties," Nordheimer said.

He called the shooting on Danzig St. "the worst of a mass shooting in this city's history."

"It instills fear in members of the public that this violence will be repeated, that it will take place essentially at random and that, when such violence does recur, perhaps they will be the next victims," Nordheimer said.

That fear remains with Yasay's sister, Jennilyn Yasay, who told reporters she has been riddled with anxiety since the shooting.

"I feel like something bad is going to happen all the time," she said.

Two other men pleaded guilty to various charges related to the shooting. Another is behind bars for seeking revenge and shooting Owusu six weeks after the mass shooting on Danzig St. One man remains outstanding.

Outside court, Det. Sgt. Peter Trimble pleaded for the public to help him find that man.

"We've exhausted all of our investigative leads to this point and hoping that someone else will come forward," Trimble said.

"I just need a little bit more, I'm that close."

Afifa Charles said she's still hurt because her daughter's killer is on the loose more than four years later.

"Too many lives have been gone, my daughter was only 14," she said through tears.

"She didn't deserve to die like that and I want him to come forward. You know who you are and you know what you did."