NEW YORK (CBSNewYork) – The NYPD says it has been working to break up gangs for years, but convincing individual members to turn their lives around can be challenging.

As CBS2’s Dave Carlin reports, those who try often encounter a lot of resistance.

Gang violence shocks the public and begs the question: What were they thinking? But critical thinking is absent, according to those who work with gang members.

“Here you have folks engaging in knee-jerk reaction that is created by the moment,” said Robert Fullilove, a professor at Columbia University’s Mailman School of Public Health. “And then boom, the rest of their lives are going to be literately guided, directed by what they did in that moment.”

Fullilove holds classes inside prisons, giving former gang members skills to turn their lives around, then help others do the same.

“A lot of them talk about what it was when they were young – this need to belong,” he said. “You’re strong, you’re united, you’re part of a family.”

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One goal of his prison instruction is to get inmates to think about becoming “Credible Messengers,” people at-risk youth can relate and listen to, Carlin reported.

“You’ve been there, you’ve walked in their shoes,” said Thaddeus Canty, of Next Steps Brownsville.

Canty was in and out of jail while in his teens. Now at 51 years old, he got out of prison two years ago having served a decade for multiple armed robberies.

“I led a life of violence, doing things that were unsavory,” he said. “Why I got into this work was to provide the guidance that they need.”

He said he speaks from similar experience, and many of the young people who join gangs lack strong role models or a sense of purpose.

“I ran with the crew,” he said. “We started just experimenting with drugs and experimenting with petty crime that escalated.”

He said more Credible Messengers are desperately needed right now.

“We need to get them on track,” he said.

Teaching gang members to think for themselves and break from the pack.