The Ten Most Wanted Men

Little Johnny's kindergarten class was on a field trip to the local police station, where they saw pictures of the 10 Most Wanted men tacked to a bulletin board.
One of the youngsters pointed to a picture and asked if it really was the photo of a wanted person.
"Yes," said the policeman. "The detectives want him very badly."
So Little Johnny asked, "Why didn't you keep him when you took his picture?"