Senseless Unfettered Brutality

Why would someone willingly blow themselves up to kill innocent people of their own religion praying in a mosque? How could a doctor, who happened to be an army officer, turn his gun on fellow soldiers? How could young men with the promise of a full life ahead of them squander all the opportunity America offers by gunning down a jogging stranger or beating a World War II veteran to death? What empty lives the perpetrators of these acts of madness must be living and what a shame that is.