Why is it that mass murderers' are usually intelligent and quiet?

[alekstra]

Every time there is one, you always hear people describing them as intelligent but quiet. Someone even said on Twitter that they were afraid of black people, but someone responded that they shouldn't be afraid of blacks, but quiet people, since quiet people are usually the crazy ones you don't wanna mess with.

[Mr. Snoid]

That's complete bull$hit. There are numerous examples of psychopathic killers who were known as social, outgoing people and charming, smooth talkers.
Being afraid of quiet people is just as ridiculous as being afraid of black people. It's a form of prejudice.
There is no single characteristic that all mass killers have in common. It's a really nasty thing to say, that "quiet people are usually the crazy ones". People who say such things have the mentality of high school bullies.