There actually is a form of mind control that in my opinion is being used to cause stupid people to commit mass murder with a so-called assault weapon: it's called advertising. Advertising is known to work very well; otherwise there would not be a multi-billion dollar advertising industry. The liberal press does not just report these stories of mass murder; they advertise them, very heavily. And the concept of copycat crimes is well known.
So you are right: there is mind control being used as you suggest; its form is just more mundane than what you might think.
And I would add that the liberal press is well aware of the effect their advertising campaigns have, since it's how they make their money.