"I feel horrible," said the former terrorist, who calls himself Abu Hurriya. "What I did was hateful, and it was wrong."
Whether Abu Hurriya achieves his goal of redemption and forgiveness isn't just a personal matter.
Counterterrorism experts say dozens of people like Abu Hurriya could be the key to stopping attacks like the one last month in San Bernardino, California.
Given their past, they have the "street cred" to appeal to would-be attackers before they become radicalized.
"There's a powerful message when someone says, 'I went down the wrong road, and please learn from my mistakes,' " said Seamus Hughes, the deputy director of the Program on Extremism at George Washington University's Center for Cyber and Homeland Security.
Peter Bergen, a CNN national security analyst, agrees. "There's no doubt the most effective people to talk to present-day jihadis are former jihadis -- those who defected or changed their minds," he said.
The government could use former radicals the way Alcoholics Anonymous encourages recovering alcoholics to guide active alcoholics, and the way public health programs enlist teen mothers to persuade young girls not to get pregnant.
There are more and more former terrorists being released from prison every year.
The Congressional Research Service reports
that in the next five years, at least 37 "formers," as they're often called, will be released from U.S. prisons. Add that to the more than 41 who've already been released since 2006.
"Formers have a bench of experience that's unrivaled because they've been there, they've experienced it; they know what it's like to be lured into extremism," said Hughes, whose group at George Washington University released the report "ISIS in America"
last month. He noted that some of the formers are not U.S. citizens, and would likely be deported to their home countries upon release.
Abu Hurriya -- a name he made up, meaning "father of freedom" in Arabic -- said he can relate to young people on the cusp of radicalization.
Abused by his mother, he left his New York City home at the age of 15 and lived on the streets, going in and out of jail on various drug-related charges.
He fell under the spell of radical leftists, and he converted to Islam in 2000. Scandals involving the treatment of prisoners at Guantanamo Bay
, Cuba, and Abu Ghraib
in Iraq fueled his hatred of the U.S. government.
Joining al Qaeda in 2004, he rose quickly and became one of the group's chief propagandists in America, establishing an online presence and actively recruiting others into the fold.
"There were many indictments, arrests and ultimately incarcerations that I played a role in," he said, expressing great regret. "Many also traveled abroad, some of whom were killed."
Calls for violence landed him in prison in 2011. He was released in the spring of last year.
Looking back, he sees that being recruited into al Qaeda was like being recruited into a cult: Members preyed on his need to belong to a family or community.
"They were kind, caring and welcoming," he remembers. "In a sense, it was brainwashing."
He said he turned himself around after getting to know law enforcement officials while in prison. "I saw they were just trying to keep U.S. citizens safe. They weren't waging a war against Islam
or against me as a Muslim. There was no conspiracy," he said.
Abu Hurriya would like to lend his expertise to help America's campaign to counteract ISIS' online propaganda -- a campaign that's been largely viewed as unsuccessful
But to help out, law enforcement will have to trust him and other "formers."
Such trust won't come easy, but it is possible, psychologists say.
"Think of how we forgive or redeem the alcoholic or the drug addict," said Joanna Lipari, a psychologist in California. "We don't blindly believe they are 'cured,' but we allow the space for their behavior to show they're redeemed."
"It's trust but verify," she added. "If Abu Hurriya is sincere, he would be willing to do just that -- be supervised and work for ongoing trust."
Abu Hurriya said he's interested in doing just that. He hopes that law enforcement will trust him and other formers, and that the formers will trust law enforcement. CNN reached out to the FBI and the Bureau of Prisons to ask if they are working with formers, or would be willing to in the future, but did not receive specific responses.
Bergen said he doesn't see the government moving toward working with formers. "I've spoken with U.S. national security officials, and they're certainly thinking about these kinds of ideas, but there doesn't seem to be any move to implement a policy at the moment," he said.
Abu Hurriya said he hopes that changes. "Extremists mistrust law enforcement, and law enforcement has Islamophobic fears. Both sides need to realize the enemy is not as black-and-white as they perceive," he said.