"He was such a good person. He'd do anything he could for anybody."

Except keep the **ing noise down.

Maybe he deserved it. In my experience, noisy neighbors don't give a ** about anyone anyway, and your sanity is not important to them one bit.
So, they drive you insane, make you lose sleep, and yet everyone acts surprised that someone gets killed? Ever hear of "temporary insanity"?
I can think of no better explanation/defense.

Nobles looks finally relaxed and quiet in the photo.