Or, more likely IMHO, it's a case of poorly trained, easly paniced, over armed, low bidder para-military wanna-be's facing a situation that even well trained professionals have trouble managing; a person with a mental illness in an agitated and seeming irrational state in highly charged context.
God only knows what they made of his wife, once the media gets the sexist 'hysterical' crap out of their systems, I'd like to hear why she wasn't allowed to approach him. There's a reason why loved ones are called in to hostage/stand off situations; they offer the best chance of a blood free resolution. I'm sure that thought didn't even get near the brains of the marshalls who killed this guy.
PC
N P Childs
'I'm Mister Bad Example, the stranger in the dirt, I like to have a good time and I don't care who gets hurt'.
-Mr. Bad Example, W Zevon