By age 14, he liked girls and playing video games like other teenagers, but they never fascinated him as much as the promise of computers.

WSJ: Tumblr CEO's mom gushes over billion-dollar baby

Since the teenagers' arrest, all the familiar theories have been rehearsed: broken homes, violent films and video games, easy access to firearms, a longing to catch the journalists' attention.

ECONOMIST: It helps if the teacher's been nice