correspondent susan candiotti is finding out, children aren't the only ones to blame here. >> reporter: the mayor goes for a nighttime stroll to prove a point. his city he says is safe. yet four times in the last year, so-called flash mobs, mainly teens, used texting and the internet to prompt gatherings that turned ugly. >> they take advantage of the large group and from that, all kind of mayhem results. >> reporter: mayhem like teens running through stores, including this macy's, merchandise destroyed, fights breaking out. in all, nearly 30 juveniles are convicted in the incidents. are the kids down there all just a bunch of troublemakers? >> of course not. >> reporter: 16-year-old charnell was there last saturday night but says she wasn't involved in any trouble. she's part of a citywide student association that add vo indicates positive activities. what do you want people to know about philadelphia and the kids in philadelphia? >> that we are not a flash mob. >> reporter: community activists blame state budget cuts that