get a local news station to film a fake amber alert with the subject of the prank being the one who stole the kid.
hijack the persons cable and play the breaking new so they can see it and get freaked out
no this might be the hard part. get the cops or even swat to show up at the house asking him release the hostage.
when he gives him self up thinking he has done nothing wrong have a cop go in to the house and walk out with the child that was on the amber alert.
now just arrest him and wait till you get him to the jail to tell him it was a joke.