Here's the full article, but below is Dr. Fast's quote.
In a family that seemed to prize privacy so much, it’s conceivable that Randy and Amy knew little or nothing about Jared’s disturbing YouTube videos and impenetrable rants on his MySpace page. And given what neighbors call Randy’s “anger management problem,” perhaps the son’s diatribes didn’t seem entirely out of place. “It's impossible to say for certain, but these kinds of shooters are usually alienated from their families,” says Jonathan Fast, associate professor at Yeshiva University’s Wurzweiler School of Social Work and author of the book Ceremonial Violence, based on his study of school shooters. “You learn to express yourself with your weapons instead of your words.”