I still haven’t wrapped my head around this.

Ive had my dog since she was a puppy. She is 4 now a 55 pound Husky mix. I put her through obedience & socializing classes at a young age. Always been a good dog. This past year she has been unpredictable around new people/children. Today her and i were going for a walk around the property my cat has always been scared of my dog (she’s always been skiddish) she was a rescue 💕.... my dog spotted my cat then chased, cornered, and killed my poor 13 year old cat. I watched this happen as I couldn’t break my dogs focus on the cat whatsoever , and wasn’t able to reach her collar as they were battling it out in a crowded shed where my cat tried to escape and hide. I even grabbed a broom to reach and try and separate them. By that point my poor cat was crying and she couldn’t fight anymore, it was absolutely heartbreaking. I finally moved some things and got to my dog to get her out of there. My question is what can i do now? I really don’t want her to be put down.. even though I’m very upset with her & cant even look at her right now, thats still my baby. Has this happened to anyone? WHAT DO I DO? Any tips on helping this aggressive behaviour are appreciated, please no negativity I’ve been through enough today i keep replaying it in my mind and beating myself up.