Starting with some background information Dogs involved: Mine(Mac)- 5-6 year old Staffordshire Uncles(Boomers and Scampi)- 10-11 year old rat terrier mix.

I have had my Mac for about 3-4 years. Third time shelter adoptee. No background on why he was out in shelters. Was living in a military base and on anxiety medicine due to the constant bombs and stuff going off.

Incident: I went to my uncle's house for dinner with Mac. Something that I have done since I took Mac in. Boomers and Scampi have always been a little weary of Mac but after a few hours no issues. He's stayed at most a week there with them while I have been on vacations with no problems. A few weeks ago I brought Mac over for dinner like usual and they were barking at him/kinda nipping like usual. Again as usual no reaction from Mac. Fast forward 30 minutes and the nipping has not gone down. I personally saw Scampi bite Mac on the neck and not let go until I pulled him off. Again no reaction. Finally a reaction happened. Mac turned around and went after Boomers. The time between start and me taking Mac off was maybe around 7-8 seconds. Unfortunately due to Macs size/strength difference Boomers was put down.

Earlier this evening my uncle came to me and said I need to volunteerly put Mac down or they will contact the proper authorities. They try to say it was unprovoked but that would turn into a he said she said situation. I love my uncle and understand the loss but I'm also adamant in the fact that Mac didn't just go out and kill his dog for no reason. The difference in size and strength is what made it lethal

I'm in Washington State. What are the options I could look towards. I do not want to put Mac down because he was fighting while other dogs started biting him.

(No I don't need comments saying I'm an idiot or my uncles an idiot or shit happens. Shits already difficult because it's family. I just want to know what proper actions I have and can look at before making my decision.)