WASHINGTON (WUSA9) -- Don't say 'no you can't' to Kevin Lopez of Waldorf, Maryland. He's heard a lot of that in his life, but 'Oh yes he can!'

Kevin Lopez is 23. He has a developmental disability. Some employers may be a bit leery to welcome people like Kevin, but with help, the Smithsonian opened its doors to this young man. That was something that changed not only his life, but the lives of everyone else around him.

The Museum of American History's World War II exhibit is where you'll find Kevin. He's a volunteer museum ambassador who's not afraid to ask you questions.

"I get to walk around, teach people, kind of like their own private tutor," Kevin explained.

For mom, just the sight of him doing this brings her to tears.

"Well … I'm so proud of him," she said.

That's because the old Kevin would never do this. He would cry, so afraid to talk to people. Kevin has Asperger's syndrome, an Autism Spectrum disorder that affects social skills we often take for granted, like looking people in the eye.

What changed?

Kevin got his dream job.

"It just brought him out of his shell. You know, it's like he was locked up for years and then somebody opened the doors and it's like, this big world just opened up to him," said Job Coach Bill Lewis.

Lewis works for the Prince George's County non-profit New Horizons. They're the ones that made this possible. New Horizons pushes to get hundreds of adults just like Kevin in jobs where they are most likely to succeed. The key is finding what makes Kevin tick.

"My favorite show, deadliest warrior. Seeing all the warriors go up against each other, that's how I first got interested in military history," Kevin explained. 

While talking history one day at the non-profit, Bill quickly discovered that Kevin is basically a walking history encyclopedia. So they pushed to get Kevin at the museum.

Bill visits Kevin on the clock, sometimes offering communication tips for the office. And sometimes...

"He's giving you some lady advice too, huh, yeah, yeah, never mind that."

This smile, the enthusiasm, the passion. Seeing Kevin overcome life's obstacles. He's not the only one who has changed.

"They, kind of give you hope. When we're supposed to be giving them hope. We're supposed to be encouraging them," Bill said.

"Before I thought, he would never be able to live on his own," said Kevin's mom.

Brianna Rossettie, who hired Kevin at the American History Museum, says Kevin is not only dedicated, but his excitement for the job is also what they need because it keeps people coming back.