A former gang leader, who pledged to change his life after more than eight years in prison, is heading back behind bars due to public safety concerns after he was shot multiple times in a Toronto park in a suspected act of retribution.

Alejandro Vivar, 34, was half an hour into leading a community workout class on July 30 when a participant opened fire. His family members, including his mother, wife and children, were in the park and rushed to Mr. Vivar's side after he ran up a hill away from the shooter and collapsed. A bystander was struck in the foot by a stray bullet.

No one has been arrested. However, the shooting will force Mr. Vivar back into custody because of concerns about public safety. When he is released from hospital, likely this week, Mr. Vivar will be returned to federal prison. Toronto police confirmed Mr. Vivar's parole has been revoked.

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His lawyer John Struthers said Mr. Vivar, whose public persona was that of a reformed man, is being wrongly punished as a victim.

"It's not fair to re-incarcerate someone for getting shot," Mr. Struthers wrote in an e-mail, adding they will fight his return to prison at a future hearing.

In 2003, Mr. Vivar faced a first-degree murder charge but was acquitted the following year. He was later arrested and given a 10-year sentence for drug and weapons possession and intent to traffic. The charges resulted from a 2007 Toronto Police raid dubbed "Project Cheddar" – a reference to Mr. Vivar's nickname, "Cheese" – in which the police seized guns and drugs, including more than three kilograms of cocaine.

In spite of his troubled past, it appeared Mr. Vivar was taking steps to turn his life around. He wrote a series of columns for the Kingston Whig-Standard, chronicling life in prison and reflecting on fatherhood and justice. Upon release, his social-media presence emphasized his new ambitions – family and fitness – which those close to him maintain were followed in earnest.

Greg Burliuk, a deacon and a former editor at the Whig-Standard, befriended Mr. Vivar after the inmate requested Collins Bay Institution start a writer's group. "It just broke my heart when I heard the news [of the shooting]. And then it broke my heart a little again to find that he might have to go back," he said in an interview on Wednesday. "It just doesn't make sense. … He's done his time."

Toronto Police have made little progress in identifying the gunman who was roughly two metres from Mr. Vivar when he opened fire. "We have no information who that shooter is at this point," said Detective Darren Worth, adding that the shooter was covered up, making identification more difficult.

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While the police say they have nothing solid to indicate the shooting was gang related, Det. Worth said he believes Mr. Vivar's past life played a role. "[He] was definitely targeted."

It is standard practice for Correctional Service Canada, which is responsible for the oversight of inmates and individuals on parole, to investigate an incident involving someone on parole and present findings to the Parole Board. A hearing then determines if parole should be revoked. Public safety is considered the top priority for the Parole Board of Canada, which does not comment on specific cases

Mr. Struthers said he is unaware of any breach in parole nor has he been given any reason for the revocation of parole, but he is ready to fight for Mr. Vivar at a future hearing.

The first condition listed on Mr. Vivar's release was that he not associate with any person he knew or had reason to believe was involved in criminal activity. "This condition will help focus your attention on the pro social relationships in your life. A breach of it will indicate an elevation of your risk of re-offending," the Parole Board of Canada said.

Before the shooting, there had been debate about the extent and credibility of Mr. Vivar's transformation from drug dealer to law-abiding citizen. The documents from his parole hearing highlight the struggle inmates face in shedding the weight of their previous lives, both inside and outside of prison.

Mr. Vivar was initially denied release on June 20, 2014, on the grounds that he was likely to commit violent acts due to his previous entrenchment in drug trafficking, arms sales and gang activity, his parole records show.

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The Parole Board documents admonish Mr. Vivar for carrying a loaded weapon when he worked as a drug dealer in the Christie Pits neighbourhood close to downtown Toronto. "You gave no thought to the fact that by carrying a loaded gun, you were increasing the risk of significant harm to anyone else in the community."

But the board also recognized Mr. Vivar's efforts to distance himself from his gang ties and previous criminal activity.

"You provided the [Parole] Board with examples of the ways in which you have done what you can to disassociate yourself from your old friends or gang members and the Board found these efforts to be credible."

Despite not identifying as aboriginal, Mr. Vivar incorporated indigenous teachings into his life while in prison. "The Institutional Elder you have been working with provided insights into his understanding of the journey you have taken, and his belief that you are serious about changing the way you will lead your life in the future," the board said.

Mr. Vivar was later granted day parole on Nov. 6, 2015, and released in March, 2016.

Mr. Burliuk worked closely with Mr. Vivar, editing his newspaper columns, which later drew the attention of the parole board. "You have also managed to walk the very fine line between appropriate and inappropriate in terms of your newspaper columns while incarcerated," the board noted in his 2015 hearing.

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Impressed by Mr. Vivar's tenacity and intelligence, Mr. Burliuk has no doubts he was determined leave behind his criminal past. "I would bet my life that he's learned his lesson a long time ago," he said. In addition to starting the fitness company and expressing strong interest in journalism, Mr. Vivar took welding classes in prison and is licensed to operate a forklift.

"People have an idea of who you are, and they're not willing to believe anything different," Mr. Burliuk said.