and hear is explicit. here's chris hansen. >> it was stupid. i'm a stupid man. >> after "dateline" confronts a potential sex offender here in rural fortson, georgia -- >> you're free to leave. >> what's going to happen? >> get on the ground! >> law enforcement working with the online watchdog group perverted-justice steps in. >> put your hands behind your back. >> even the u.s. marshal and secret service are involved. remember scooby-doo atl-101? 23 yrlds dennis koulson? he made plans to teach new sex tricks to a girl he was told was 15. >> oh, my god. i'm a [ bleep ]. >> after he's arrested, he's put in an unmarked car and taken to this ems station, where he will be questioned by law enforcement. his car is searched. police find directions to the house, along with condoms and marijuana. >> more tv in here? >> coulson is then brought to a room where he waits to be interrogated. that's where he meets harris county sheriff mike jolly, who finds out this isn't coulson's first run-in with the law.