Investigators have linked three homicides and six shootings between Sept. 4, 2011 and Aug. 10, 2012 to the Galloway Boys gang, Det.-Sgt. Brett Nicol told a news conference.
The group's bloody battles with a rival gang nearly a decade ago culminated in a massive police sweep that saw several ringleaders imprisoned.
"It did hamper their criminal involvement in this end of Scarborough," Nicol said of the former eastern Toronto borough.
"But slowly, members got out," and came to mentor the new generation — many of whom are now sought in this latest string of attacks, Nicol said.
"This recent violence is based on, as they refer to it on the street, a beef," which started about a year ago, he said.
Fourteen-year-old Shyanne Charles of Toronto and 23-year-old Joshua Yasay of Ajax, Ont., were killed when gunmen exchanged fire at a block party on July 16 that was attended by about 200 people.
Twenty-three others were sent to hospital with gunshot wounds after what police called the worst mass shooting in Toronto's history.
Det.-Sgt. Peter Trimble said "a small group of young punks, approximately five to six people... were involved in the shooting," which he said stemmed from a confrontation between the Galloway Boys and a group from the nearby Malvern neighbourhood.
The deadly rampage rocked the city and reignited the debate over how to tackle gun violence and help disadvantaged youth.
Simmering tensions between police and some at-risk communities — such as the Danzig Street complex where the shooting took place — also came to the surface.
Police have since made two arrests in the attack.
Nahom Tsegazab, 19, was charged with reckless discharge of a firearm. Police said Tuesday he belongs to the Galloway Boys.
Shaquan Mesquito, 18, from the Malvern area, faces charges of threatening to cause serious bodily harm before the shootout.
After several highly publicized appeals for information that yielded many tips, police said Tuesday they have hit a major hurdle in their efforts to make further arrests.
"It was such a horrific incident that it generated emotion, that people wanted to speak to the police, people did want to co-operate," Nicol said.
"The only thing is, the people that want to co-operate might not have been the eyewitnesses that we need to ultimately prosecute these people."
Trimble also said that people who were wounded are not co-operating with investigators.
He said police have recovered firearms and shell casings but they still need witnesses to come forward.
In a separate incident, D'Mitre Barnaby, 24, died of gunshot wounds on Dec. 30, 2011 in a shooting that Nicol said was a case of mistaken identity as Barnaby had no known gang affiliation.
The homicides and several other shootings occurred in east-end Toronto in the area of Galloway Road, which is home to the Galloway Boys.
"The investigators believe that the conflict between the Galloway Boys and other neighbourhoods in the Scarborough area... is being fuelled by the Galloway Boys' propensity for violence, their ability to obtain guns and their willingness to seek revenge," Nicol said.
"We have some information that the shooters in these incidents are vying for the leadership within the Galloway Boys group."
The news came as no surprise to some in the tight-knit community, who said they were aware of a gang presence in the area.
"I don't fear the Galloway Boys and I have a few friends in this area — I don't think they fear them because we all live here, we see them on a daily basis," said Stephen Ford, who lives near the social housing complex where the shooting occurred.
But he admitted the threat of retaliation has weighed heavily on others in the neighbourhood.
"A lot of the neighbourhood is basically trying to keep to themselves and stay quiet, which shouldn't happen if they want the change, they need to voice their opinion," he said.