He was already known to police when he was wounded during the infamous Danzig Street gun battle in Scarborough four months ago.

Then, on Sept. 2, he was shot a second time as he rode his bike on nearby Chester Le Boulevard, in what police suspect was retaliation stemming from the Danzig Street violence, which left two people dead and 23 others wounded.

Shortly after came an arrest on cocaine-trafficking charges.

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And while he was awaiting court dates for that, the youth was arrested late Thursday night, this time accused of two counts of second-degree murder, plus 24 other charges, all stemming from the Danzig Street bloodletting – the worst mass shooting in Toronto's history.

He is also an alleged associate of the Malvern Crew, whose long-time feud with the rival Galloway Boys is believed to have been the catalyst for the events that muggy July night, which shocked the city.

He is 17, his name shielded by the Youth Criminal Justice Act.

He is the third teenager to be charged with murder in connection with the mass shootings, which erupted when a street barbecue at a public-housing complex was allegedly hijacked by the Galloway Boys, who take their name from a street a few minutes' walk away.

"It's actually alarming that we would have a 17-year-old youth charged in such a callous act of violence," said Staff Inspector Greg McLane, who heads the homicide squad.

Along with the 23 party-goers left wounded, Shyanne Charles, 14, of Toronto and Joshua Yasay, a 23-year-old barber shop owner and aspiring police officer from Ajax, were killed.

"He was in possession of a firearm and the allegations indicate he was responsible for some of the injuries that day," Staff-Insp. McLane said of the youth.

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"Is it an indicator of things to come with younger and younger people being involved in gun violence? I don't know, I can't speculate, but I would have to say it's very concerning."

Staff-Insp. McLane was asked if detectives believe the youth showed up at the barbecue "with a purpose."

"You could say that," he replied.

The youth was arrested a few hours after similar murder charges were filed against Nahom Tsegazab, 19, an alleged Galloway Boys associate.

And earlier this month, Shaquan Mesquito, an 18-year-old from the Malvern area also known as "Bam Bam," was charged with two counts of first-degree murder, one count of attempted murder, reckless discharge of a firearm and 23 counts of aggravated assault.

Mr. Mesquito had been behind bars since July 27, nine days after the shooting, and was initially charged with uttering threats and possessing a .22 calibre revolver.

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Meanwhile, detectives are still anxious to speak to a man known only as "Juvi," who is believed to have been at the crime scene that night.

Police suspect there were at least four shooters during the gunfight, and Staff-Insp. McLane said Friday the investigation is far from over.

"We've had co-operation from the community, it's been somewhat of a challenge, for obvious reasons: [People] perceive these individuals to be very dangerous and violent."