Sad thing is, person doesn't even have to look creepy to begin with.
There been cases of common Joe average, like someone in your society that you wouldn't expect to be that type of person, before it is too late. Had that incident around where I lived where someone at a school I went to was being molested by his musician/teacher. The kid(technically young teenager) never told anyone about it and finally people found out about it after the kid off himself.
It was a big shock all around. As again no one knew that was going on and again the teacher didn't look like that type of person to begin with. But that is just a sad outcome to victims to those events that keep quiet about it. At least the teacher was arrested and locked away, but maybe if victim spoke out or something ahead of time that tragic end could of been avoided.