In Oregon, the "I was in fear of my life and I thought I saw a potential weapon in his hand" is enough to work with to avoid manslaugher charges. You may still have to defend your actions in front of a jury but that's not probable.
Story 1: Cornered cop blows away crazy maniac at our local community college. The perp had a Sharpie...LOL! It was daylight so there went the excuse of "it was dark", which always helps the cause but the matter went before a grand jury, which did nothing.
Story 2: A guy I went to HS with back in the day was dealing weed a few years later. Some guys broke into his house while he was home. He blew them away. No charges for the killing were made.
Story 3: Big White ******* in his 20's stirs up shit in a bar. A Mexican small guy didn't like the way the BWA was behaving. Out in the parking lot the BWA charges at the Mexican, who had a gun. The Mexican blew him away and fled the area. He was arrested in SoCal, brought back here and charged with killing the BWA. He was convicted. Moral learned here is that if you are a real Mexican national and you defend yourself with deadly force against a BWA, you're toast.
Story 4: Biker-type guy has someone confront him in a run-down residential neighborhood by his home. He shoots the guy dead. The cops ruled it self-defence at the scene and nothing more happened.
Odds are good if you kill a POS in Oregon that you will not have too many problems and even if it goes before a Coos County jury, as long as you have a good enough story and you aren't a Mexican national, you'll be fine.
The real problem is in cleaning up the blood and patching up for all the bullet holes in your car afterwards....LOL!
By the way, I knew of the BWA and if I had been on the jury, the Mexican would have walked. The BWA brought on his own demise.
Rick