Francisco Sanchez said his days as a gang leader on Chicago’s West Side were over.

At 50, he said he had seen numerous lives ruined by violence — young people losing the best years of their lives to prison; children left without parents in the name of petty disputes and turf wars. That’s why he became something else: a leader in an organization committed to ending gun violence.

But last week, federal prosecutors charged that Sanchez’s redemption had been a sham. They said that at the same time Sanchez was moonlighting as a supervisor at CeaseFire Illinois, he was heading up one of Chicago’s most violent street gangs, the Gangster Two-Six Nation.

Sanchez, who was previously featured in a Trace story about Chicago violence interrupters, was arrested last week as part of a joint state and federal roundup of 45 members or associates of the Gangster Two-Six Nation. He was charged with illegal possession of a firearm by a felon.

An affidavit attached to his complaint asserts that Sanchez is, in fact, the leader of the gang, which started in his neighborhood and is now active in six states. The accusation is a punch in the gut to the already beleaguered violence-prevention organization. Budget cuts last year forced CeaseFire Illinois to close 13 of 14 Chicago sites where its outreach workers, known as violence interrupters, patrolled. Since then, the group has subsisted with just eight full-time employees on a few small grants from private donors.

The arrest of one of the chapter’s highest-profile remaining workers renews questions about whether using ex-gang members and felons as outreach workers is worth the risks associated with doing so.

Sanchez couldn’t be reached for comment. Dennis Doherty, his lawyer, said that the gang-leader allegation is false, and so is the gun-possession charge.

Charlie Ransford, director of Science and Policy for Cure Violence — the umbrella organization that includes CeaseFire Illinois — didn’t directly address the allegations about Sanchez. In a statement, he said that the credibility that former gang members and felons offer is worth the risk of hiring them.

“Although relapses occasionally occur, they are rare,” he said. “The reality is that the health approach to violence prevention saves thousands of lives across the U.S. and the world every year.”

For nearly two decades, Chicago’s violence interrupters have been working to stop violence the way you stop the spread of a disease — by seeking out the people who are most likely to spread it and trying to intercept them. The group hires people who are respected on the streets — often because they are themselves one-time gang leaders and felons — and asks them to use their credibility to convince people not to retaliate or lash out after a shooting or other violent crime.

Several studies of Cure Violence programs have shown that they can be effective. But the high-profile arrests of workers has also proved to have a chilling effect on the willingness of public officials to support violence-interrupting programs.

At least seven CeaseFire Illinois workers have been convicted of crimes since 2000. In 2013, Mayor Rahm Emanuel opted not to renew a one-year, $1 million contract for CeaseFire programs in two Chicago neighborhoods, after police expressed concern about what they said was a lack of cooperation by the group. The decision also followed the arrest of the group’s director on domestic battery charges — charges that were later dropped.

Jeffrey Butts, a professor at John Jay College of Criminal Justice who is studying the effectiveness of Cure Violence, said it is unfair to argue that the arrest of an outreach worker means that the entire program should be disbanded.

“Everyone loves to jump on this story every time,” Butts said. “We never do that when a police officer shoots an innocent person. We may say, ‘We should be more careful who we hire,’ or ‘We need to train people better,’ but we never say ‘We should stop having police officers patrol our streets.’”

Butts also pointed out that the very thing that makes Cure Violence effective requires that it employ people with gang and criminal histories. When a member of Alcoholics Anonymous goes back to drinking, the validity of the whole program is not questioned, Butts said.

The Trace spent a day with Sanchez this past winter as part of a profile about what remains of Chicago’s violence-interrupter program.

Sanchez said that he never knew his father and that his mother died when he was 5. He grew up on the streets of the Little Village neighborhood and was a gang chief by the time he was a teenager. He later served 25 years in prison for murder.

We accompanied Sanchez as he patrolled Brighton Park and Little Village. During that day, he checked in with a couple who were trying to quit gang life for the sake of their two young children. He also drove the streets looking for unusual activity and chatted with residents who rolled down their car windows to say hello to him.

“I took so much from this neighborhood,” said Sanchez, who was released from prison about seven years ago. “If I can help now, I’m there 100 percent.”

When The Trace interviewed Sanchez, he spoke frankly about the lure of the streets. He said he understands when young people tell him how addictive the rush of gang life can be. Even when he was in prison, young people in West Chicago knew his name, he said.

“It’s sad to say at this age, I feel like the street still calls me,” he said.

According to the federal complaint, police served a search warrant on Sanchez at night, and found a Colt model 1911 .45 caliber pistol in a metal box inside a book on top of a dresser that appeared to contain Sanchez’s belongings. An affidavit by a special agent for the Bureau of Alcohol, Tobacco, Firearms and Explosives attached to the complaint states that a confidential informant, who has provided reliable information in the past, said Sanchez is the national leader of the Gangster Two-Six street gang. That informant has also been convicted of murder, and was paid more than $30,000 for the information he provided, according to that affidavit.

Police and prosecutors declined to comment because the case is ongoing. The affidavit by the ATF agent notes that information was based on interviews with the confidential source, consensual recordings and physical surveillance. The agent noted that he had not included everything he knew about the investigation in the paperwork.

Doherty, Sanchez’s lawyer, said he’s known Sanchez for years. He said that Sanchez has asked him to speak to young people in West Chicago about the horrors of prison, and that Sanchez has done small jobs for him — like delivering documents for $50 a job. No gang chief would need to deliver documents for such a paltry sum, or work for Cure Violence for a salary of about $30,000 a year, Doherty said.

“I think they’ve made a sad error here,” he said.