How do you define "stupid"?

Apparently, it should be defined as this guy. He is on a 10 year probation for having killed a 6 year old girl when he was 12. He got 5 years added on in 2004 for brandishing a knife. So what does he do now? He pulls a gun on a Dominos Pizza Delivery guy! Sigh. This guy should be locked up for his own protection, if not for society's.