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JOHNSTON, Iowa — Catching child predators via social media is a growing trend nationwide, and a Johnston man is doing it here in the metro.

Colin McCarty travels around the metro trying to catch child predators by posing as a young girl on social media.

“Most of it comes from within my past. I have had elders or people that I have worked with or coaches that I have had in high school who have tried to groom me,” said McCarty.

McCarty makes the first connection through a mobile application called Whisper.

“I never make first contact. They`ll contact me and we will talk, and I will eventually tell them my age and that is kind of the barrier. Are they going to continue to talk to me knowing how old I am, or will they say nope and block me?” said McCarty.

McCarty captured a recent undercover sting on video. He met a 31-year-old man in Johnston. McCarty says the man thought he was meeting up with two teen girls.

McCarty isn’t a police officer, but he turned this video over to Johnston police who say they are investigating.

“I have caught two other guys here in Des Moines, the area of Des Moines. And the police seemed not to be too interested. I am not speaking against the police. They don`t make the law. They just enforce it, but according to them, it is very hard for them to prosecute something like this,” said McCarty.

That is because in Iowa, the crime of enticement has occurred when a person acts with the intent to commit an illegal sex act upon or sexual exploitation of a minor under the age of 16, and that can be hard to prove.

“In that video, I didn`t see anything that would indicate that this guy is breaking the law. The issues really come down to you are doing this with the best of intentions. You could be endangering your own safety,” said Des Moines defense attorney Nick Dial of Dial Law Office.

Dial says social media vigilantes should think twice about it.

“There are a lot of unknowns out there for people that don’t take on the vigilante role. If you think you found something illegal, you should call police,” said Dial.

But McCarty is on a mission. He says he has already turned over 15 cases to police. And though we don`t know if any of those cases resulted in prison time, he is satisfied with the publicity.

“It takes everything away from them; their job if they are a provider. Their wife will leave them. They are basically out on their butt after they get caught in my sting,” said McCarty.

Channel 13 reached out to Johnston police for comment but have not heard back.