After serving nine tours of duty in Iraq and Afghanistan, he now has a new target - child predators.
Zepeda, 29, is part of a 17-member class of veterans trained in computer forensics and sent to Immigration and Customs Enforcement field offices. They aren't paid, and there's no guarantee that they'll have a full-time job when their one-year stint ends.
But the interns are finding the purpose of their new mission outweighs financial considerations.
"I love challenges. And I have a family of my own," said Zepeda, whose military career was cut short by a hand grenade and the 25 operations that followed. "I feel I'm still serving my country and protecting my family at the same time."
For Shannon Krieger, who was in the Army and is now assigned to an ICE office in New Orleans, "This was a new fight I could sink my teeth into. That's what really I was looking for. I wasn't just going to take a job so I can have a paycheck."
Federal officials say a children's lobbying group, PROTECT, pitched the idea of incorporating wounded veterans in the fight against child pornography. ICE Special Agent Patrick Redling said the agency, where veterans account for 30 percent of the workforce, ran with the idea.
"They built their career upon fighting for this country and keeping citizens of this country safe," Redling said. "What better to get somebody already with that mindset into a program where it's another battlefield, very similar, but you're keeping our children safe. You're taking predators off the street."
The agency relied on the U.S. Special Operations Command to get the word out to wounded service members transitioning out of the military or already separated. The veterans were given about 11 weeks of intensive computer and legal training before being assigned to an ICE field office.
Even though they're not getting paid by ICE, the majority of those on the team are receiving disability compensation. Many also get a monthly stipend from the Department of Veterans Affairs for educational expenses.
In exchange, they're gaining expertise in computer forensics, a skill that's in high demand with law enforcement agencies, and one that should lend itself to job offers once the internship is completed.
In general, the veterans work in a lab and scour the computers and flash drives that agents in the field confiscate when conducting a search warrant. The veterans have two priorities: analyze the evidence to assist in the prosecution of a suspect, and help determine if there are children still in harm's way who need to be rescued.
The veterans also are called on to help agents carry out a search warrant. Zepeda said that's how he spent his first day on the job.
"We went on a raid and it was almost like I never left the Army," he said. "It was like, 'I'm ready. Let's do it.'"
When it comes to child pornography, a child is defined as any person under the age of 18. The Department of Justice said 2,331 defendants were charged in federal court during the past fiscal year with producing, distributing or receiving child pornography. During the previous four years, the number of federal defendants charged with child pornography offenses ranged from 2,012 to 2,254.
The veterans say they've already seen what Krieger called the "real dark side of what humankind can do."
"I'm talking about young kids, 18-month olds, toddlers. This is some of the most horrible stuff I could conceive of imagining and I'm looking at it on a daily basis," Krieger said.
ICE Special Agent Brian Widener said part of the interview process was spelling out for the veterans the types of materials they would have to view. Each veteran was assigned someone who will check on them at least once a month to make sure they are doing OK. The veterans can call their case manager any time they find themselves needing to talk.
The veterans said their combat experience is proving to be an asset when it comes to dealing with the emotional toll of the job.
"I'm able to turn a lot of things off," Krieger said. "If I couldn't, I'd probably have gone crazy."
Zepeda said that, in his time in Iraq and Afghanistan, "I've seen it all. Trust me."
He said he tries not to think too much about what he sees on the job.
"You just move on," he said. "You know what you're seeing, but you're not getting personal with it."
Justin Gaertner, a Marine Corps combat engineer who lost both legs in Afghanistan serving as a lead sweeper for roadside bombs, said he had to think long and hard before taking the internship. He worried the work could make the mental aspects of his recovery more difficult.
In the end, he said the satisfaction of possibly saving a child's life or putting a child predator behind bars outweighed the negative considerations.
"My time got cut short in the service. I wanted to continue serving my country, and this was my way to do that," said Gaertner, 24, the youngest member of the group.
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