Largo, Florida (CNN) Ret. Sgt. Tom Block is sitting in the classroom, looking restless. He and 23 other highly specialized, highly coveted candidates are all vying for a job where they will be exposed to some of the most horrifying images humanity can produce.

Each candidate is a veteran of America's recent wars. Many were part of the elite special ops forces. They conducted daring, covert missions to take out America's most dangerous enemies.

Many were wounded in battles across Afghanistan and Iraq. And now that their military career has come to a close, they are looking for a second chance to find purpose in their lives back at home -- and the answer could be the HERO Child-Rescue Corps, saving at risk kids.

J. Christian, CEO of the National Association to Protect Children (Protect) , says: "A lot of the individuals who come into the HERO Corps are truly individuals who have lost their mission on the battlefield."

Christian, an Army Ranger who fractured his spine during a mission in Afghanistan, says many of the veterans who come into HERO are hoping to regain that something they lost when they left the service.

Block is hoping to get a second chance to "go after bad guys again."

"In one second their entire life changed. When that happens, I know from personal experience, you start to wonder, what can I now do? And once you find this opportunity, you know it's truly your opportunity to step back into that role."

The HERO -- Human Exploitation Rescue Operative -- program is designed for wounded, injured and ill veterans to receive training in sophisticated computer forensics, to join federal agents fighting against online child sexual exploitation.

Developed by Protect, in conjunction with Homeland Security Investigations (HSI) and U.S. Special Operations Command (SOCOM), the veterans receive 11 weeks of intensive training and 10 months of on-the-ground experience.

They work alongside law enforcement teams executing warrants and serving as computer forensic analysts as part of a year-long unpaid internship. That means scanning computers and external hard drives on-site to determine whether the suspect possesses child pornography and, critically, whether the suspect is also producing child pornography.

During that year-long internship, HERO Corps trainees will sift through thousands of disturbing images of adults sexually assaulting children.

"You see groups of children being abused at levels the average American cannot fathom. If you imagine an infant getting gagged and bound and tortured, it's not a rare occurrence to come across," says Christian.

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According to Christian, the U.S. is the largest producer of child pornography in the world. He also points to research showing the U.S. is home to the most commercial child porn websites

The National Center for Missing and Exploited Children says its Victim Identification Program, which aids law enforcement in efforts to locate and rescue child victims, has reviewed more than 158 million images and videos , since 1998.

In 2008, an ICAC Task Force network identified over 300,000 unique computers engaged in trafficking child pornography . A study by the University of New Hampshire found that 55 percent of those who possess or trade child pornography, are hands-on offenders.

Block says: "It's horrible. But that's my motivation, that's my drive. To get after these guys. Get them off the internet and hopefully I can get to them before they get to another child."

Now in its third year, HERO Corps hopes to place its 100th veteran this year. Once embedded in a law enforcement agency, just one HERO can stop or prevent the exploitation of as many as 50 children per year, by providing law enforcement with the digital evidence they need to identify and locate endangered children.

Cpl. Justin Gaertner (left) and Sgt. Gabe Martinez (right) were both injured in action, both are amputees in wheelchairs and both are joining HERO Corps.

While the mission may be similar -- finding and capturing bad guys -- the method will be much different.

As a HERO trainee, Block will be in a support role, mostly analyzing computer files. It's a far cry from his last, as a soldier in the 3rd Battalion, 75th Ranger Regiment, serving in Afghanistan.

Block says: "I wanted to be a Ranger my entire life because it's the greatest job you could ever hold. I mean they literally paid you to carry a gun, jump out of an airplane and just be awesome in general."

But defending your country doesn't come without its share of danger. Sgt. Block's life changed on October 6, 2013, when he and fellow Rangers embarked on a direct-action raid to root out insurgent bombing attacks.

Block spotted a couple in a courtyard and ordered the two to put their hands in the air. That's when one of the insurgents detonated an explosive strapped to her body.

He says: "From what I'm told the explosion leveled some of the house. The only thing that separated me [from the suicide bomber] was the guy I was holding onto. And all of his bones ended up in my American flag that was wrapped around my plates and melted. And I think I got a chunk of him in my cheek, because I have shrapnel lodged in there."

In 2014, Block was named the Army Times' "Soldier of the Year" for courage displayed on the battlefield and his ability to inspire and motivate other soldiers during his rehabilitation.

But like so many who return home, Block struggled to find a purpose and mission once his military career came to a close.

That's what brought him to his classroom in Florida, and the HERO Corps which offers a new path to doing what he does best.

"It's an opportunity for me to go after bad guys again. The complete scope of the crime is a lot more than people probably think," he says.

And while doctors managed to save the vision in Block's left eye, look at his right eye and you will see something unusual -- a prosthetic bearing the Captain America shield. Sgt. Block is turning his setback into a statement.

Block says: "He doesn't like bullies. And neither do I."

Having vision in only one eye, makes staring at a computer screen all day challenging. But Block imagines one day pointing out the shield, to comfort a frightened child who he and a team of law enforcement officers have just rescued from an abusive situation.

"I'll be honest, looking in the mirror can be tough sometimes," says Block. "But you keep your faith, you keep your confidence, and you go out there and try to make somebody else's life better. It's what you do after-the-fact, and I think I'm trying to do a pretty damn good job."