There's an email circulating about a pedophile who has been preying on kids in Har Nof, Jerusalem. A neighborhood activist asked Rabbi Moshe Shternbuch if police could be called to report the pedophile if he trued to grab a child on Shabbos – which apparently happened last week.
Rabbi Shternbuch said police should be called, even on Shabbos, and that pictures can be taken of the pedophile even on Shabbos, but added that when possible, the call and the photography should be done with a shinui, meaning that a person should, but only if possible without delaying, make a change in how s/he would regularly dial the phone or take the picture. (Halakhicly, a shinui should not be used if it would delay reaching police or if it would reduce the quality or quantity of the pictures taken.)
A prent asked Rabbi Shterbuch about publicizing the existence of the pedophile,and Rabbi Shternbuch said it should be publicized.