Why?

I know I'm not the only one asking this question today. Why would someone just wake up one morning and decide "I'm going to school today with a gun and I'm going to kill anyone and everyone I can." Just senseless killing...that's all this seems to be. My heart hurts for all those at Virginia Tech and their families. I've prayed and I know God knows a reason...Why?....Why do innocent people have to die?...Why can't you send your kids to school without worrying about them not coming home?...I just don't know