Where did the title, "Killer Angels," come from?

I'm glad to see that I'm not the only person that is finishing their last entry on the day before it was due! :) I was fascinated by where the author, Michael Shaara, got his title for "Killer Angels." Colonel Chamberlain, a professor of rhetoric at Bowdoin University, is recalling a speech memorized from Shakespeare's "Hamlet" Act II, Scene 2 that he shared with his father when he was in school:

What a piece of work is man! how infinite in faculty!
in form and moving how express and admirable!
in action how like an angel! . . .

After finishing the scene, his father's comment, "Well, boy, if he's an angel, he's sure a murderin' angel."

As I recall Hamlet's soliloquy, isn't he trying to reconcile his belief in the "divine potential of mankind" and his grim surroundings? That seems to have been the message that Chamberlain's father was trying to give him. Thus, Shaara's grim reminder to us all in the title of his book. Isn't it interesting that we have taken that same quote today and have given it a completely negative connotation?? "What a piece of work." I too share Shakespeare and Chamberlain view of humankind!