Likely the cop will be be ruled justified because he will probably be believed in thinking he saw a weapon (even if erroneous). So, probably determined “lawful but awful”.
I’m with most commenters on Donuts site. Probably an ND. Cop really should catch a manslaughter charge, like any of us would.
Guessing the cop will be encouraged to retire in exchange for no charges. I hope I’m wrong and gets charged.