Publicly calling out a POSSIBLE sexual predator.

So the other day my kids old preschool teacher made a Facebook post with a picture of a man, sitting at a library computer. A public library, right down the street from my home, where all the middle school kids hang out after school and wait to be picked up. She titles it "watch out for this guy" Apparently he was looking up pictures of young girls. She said she stood behind him for several minutes and watched him looking at these pictures, and then went to the library staff, where she was told they couldn't do anything about it. She proceeded to call the police, who also told her they couldn't do anything. I guess because they were just pictures of girls, and we're not deamed "inappropriate". Since her daughter and her friends kids hang out at that library after school, she took a full faced picture of this man and posted it on Facebook, urging parents to watch out for him. My question, is what she did ok? How do you think library staff should handle the situation?