I have never even heard of this. However, the pupils of my eyes will go coal black if I'm angry or if I just want to freak someone out. When I get angry enough for that to happen whomever my anger is directed at and even people who aren't even in front of me begin to fear for their lives. For example: My baby sis told me one night when she was 14 that she had been date raped (no she didn't say it that way, she just told me what happened). The look on my face when she got done had her cowering in a corner on the floor in a fetal position. Personally, I think his brain overwrought the eyes out of pure fear; but the fear was real so he was obviously in real danger. Which leads me to suppose it was his gut reacting to a prank. The fact that the other boy was nervous and kept looking around says he was a real flesh and blood kid, his friend sounds like a sociopath or psychopath. The second boy probably lives out his fantasies of being big and bad vicariously through his friend who really is bad.