Why?

Why did Cho Seung-Hui want to kill so many innocent fellow students? I presume it was anger of some dimension. but what makes someone so angry they feel the need to kill - and kill randomly those one associates with?

On the question of why - why is driving in Sri Lanka so testosterone-based? you often get the sensation that people (of both sexes) measure themselves by how aggressive they are behind the wheel of a vehicle. My friend Nirm used to tell me to just let them go in fact even be more polite - this often confuses them.