They were considered leaders of some of the biggest, deadliest gangs in Chicago.

Willie “Minister Rico” Johnson, Francisco “Smokey” Sanchez and Melvin “Head” Haywood all did time in Tamms Correctional Center, a Supermax prison where gang leaders were held to keep them from communicating with their underlings.

Now, they’re back on the street after completing prison terms for murder. And they’re communicating with gang members again — but this time  as “interrupters” for the anti-violence group CeaseFire. The job pays about $33,000 a year, records show.

CeaseFire has been celebrated for its success in stopping street violence in a widely seen documentary, “The Interrupters,” but many cops still view it with skepticism since some of the group’s employees have been charged with serious crimes while working there.

Gary Slutkin, the founder of CeaseFire, said job screeners for the program make sure employees like Johnson, Sanchez and Haywood are no longer active in gangs. Still, the screeners are looking for employees who can speak to gang members in the language of the streets and can gain their trust, Slutkin said.

“Our job is to stop the shootings . . . and change people’s thinking,” said Slutkin, whom Gov. Bruce Rauner recently presented with the Order of Lincoln, the state’s highest award for public service.

“Some are influenced by someone who was a leader.”

In recent years, Slutkin has been flying around the world, replicating the CeaseFire model in Europe, Africa, the Middle East and South America. He said he hasn’t directly managed Chicago’s CeaseFire program since 2007 and wasn’t familiar with the particulars of the three men’s pasts. But he recalled one award ceremony in which Haywood received a CeaseFire award for a large number of shootings he was credited with preventing.

“He brought his mother, he was so proud of what he’s doing now,” Slutkin said.

All three men were “nation leaders” of their gangs, according to the Chicago Crime Commission. Johnson, 66, was a leader of the Conservative Vice Lords. Haywood, 65, was the “co-chairman” of the Gangster Disciples. And Sanchez, 48, was a leader of the Two-Six gang, according to the commission’s “Gang Book.”

“I am not saying that someone cannot turn their life around,” said Joseph C. Ways Sr., the former second-in-command at the Chicago division of the FBI and now the executive director of the Chicago Crime Commission. “If, in fact, they have done that, we wish them all the success in the world.”

But Ways isn’t sold.

“We don’t have to go all that far back into the past to see some of the past paid employees of CeaseFire who have been arrested for their continued criminal activity,” he said. “It is somewhat suspect why some of these quote-unquote ‘former gang leaders’ are making their way to this organization.”

Slutkin, a medical doctor who once worked for the World Health Organization, founded CeaseFire about 15 years ago in Chicago to cure violence with similar strategies he used to attack disease epidemics. Last year, a study by the University of Illinois at Chicago found CeaseFire interrupters were effective in reducing violence in the Grand Crossing and Ogden police districts. There was a 38 percent greater decrease in murders and a 15 percent greater decrease in shootings in those districts than in comparable districts from mid-2012 to mid-2013, the study found.

Mayor Rahm Emanuel had provided $1 million in funding for the work in those two districts, but the city contract wasn’t renewed.

CeaseFire, which is supervised by UIC, continues to operate in Chicago with other financing. Slutkin said the group conducts about two interruptions of potential shootings every day in the city.

Peer pressure is the greatest motivation for violence, Slutkin said. The key is to change attitudes that gun violence is the best way to solve conflicts, he said.

These days in Chicago, most shootings aren’t the result of a gang leader ordering a subordinate to kill someone else, Slutkin said. More often, they stem from petty conflicts over girlfriends or debts, he said.

CeaseFire interrupters try to stop retaliatory shootings, which can mushroom out of control, Slutkin said.

In an interview with Chicago Sun-Times, Willie Johnson, one of those interrupters, said he joined CeaseFire because of “the need for our kids to become better men than we were.” He said he’s helped prevent retaliatory shootings in the South Shore and South Chicago neighborhoods.

“I’m not trying to find out who did the [original] shooting. My job is to stop the problem that might lead to another shooting. I’m not going to the police and exchanging nothing with them. I am going directly to the community. The mayor pays the police, not me,” he said.

Asked about his past with the Vice Lords, Johnson calls himself a “former influencer,” but won’t discuss what position he held in the gang. He said he’s focused only on stopping the shootings that led to more than 400 murders in Chicago last year.

“Your deeds outshine your words,” he said, adding, “I’m not going back to the pen for you or nobody else.”

Johnson was 23 when he was arrested for fatally shooting his brother-in-law, Homer O’Neil, on March 25, 1970, on the West Side. Newspaper accounts said O’Neil was trying to break up a fight between Johnson and a third man when he was killed. Johnson says he shot O’Neil in self-defense but was convicted because he couldn’t prove it.

Johnson said he was behind bars until about a year and a half ago, including a nine-year stint at the now-shuttered Tamms Correctional Center, which he called “dehumanizing” because inmates were placed in isolation.

Johnson said he met Larry Hoover — the notorious chairman of the Gangster Disciples and an enemy of the Conservative Vice Lords — in prison in the early 1970s.

“I didn’t even know him. Didn’t like him, didn’t care too much. And we grew to be the best of friends,” Johnson said. “We learned that together we could do greater things than destroying each other.”

He said he and Hoover discussed ways to broker peace among gangs in Chicago.

In the 1990s, Hoover was moved to a federal Supermax prison in Colorado, where he remains.

Johnson said most young gang members on the street are unaware of his reputation with the Conservative Vice Lords. “They don’t know who I am — but I know what they are going through,” he said.

Johnson said he’s “breaking down the myths” about how former gang leaders are expected to act.

“What’s important to me is that a child not become another Rico Johnson, spending 42 years in a cell,” he said, acknowledging that he was a “rotten apple” when he went to prison.

“I don’t care what gang a young man is from or nothing. I just see a young man who needs help,” he said.