need to write an essay about crimes where the culprit was the person least suspected because he/she seemed nice or isolated. For example there was a case i remember where a isolated high school student took a gun to school and kill three students. Nobody would I have ever guess that he would do such a thing for he was shy and quiet. But I really need more examples

I really don't follow the news alot so I really can't remember many examples of such cases. but if you remember any or have a link to some I'll be very grateful.

thanks

ps; this actually relates to A Rose For Emily, but its okay if you havent read the story