CARY, N.C. -- A Wake County substitute teacher is being recognized for helping to catch a registered sex offender at an Apex park.   

Karen Donalson was in the park with her grandson when a man sitting nearby started asking sexually explicit questions to two teenage girls.

She called 911 and it turned out the man was a convicted sex offender. He was arrested shortly after her call.

Wednesday, Apex police gave Donalson the Citizen Challenge Coin at Green Hope High School where she is doing her third long-term substitution.

The coins are usually given on the spot by an officer to a citizen they believe has helped the public in some way.

Today marked the first coin police have given publicly because they wanted to share Donalson's deed with her students so they in turn can also act if they are in a situation they needs police assistance.

Donalson shared a quote from President Ronald Reagan that helped her go ahead and make the call.

"Evil cannot prevail when good people do the right thing,” she said. “Notice he didn't say when strong people do the right thing or when the smartest people do the right thing. No, he said when good people do the right thing."

Apex police say, like Donalson, if you see something, say something.