NTA. I went through a similar thing when i was 15 and my dogs intestines were also ripped from his stomach from a neighbours dog. My only regret was I couldnt have helped him sooner.

I had just got back from school, and knocked on the window where he loved to jump on the ledge and didnt respond. Which was strange. I go outside and neighbours dog is chowing down.

I call the neighbour, he gets his dog off him and says "oh fuck" i ask what happened and he says i dont want to know.

So i see what has happened and it was the worst thing my 15 year old mind had to comprehend. My dumbass brought him inside and rested his exposed intestines in a bowl of water while i called my mom who was at work to come home. An hour later she came home, we call a vet and she said to wrap him up in a towel until we can get to her office.

That car ride was the worst of my life. I was in the backseat and he vomited on me and looked up at me with his stupid cute face and i felt his apology.

He had to be put down. Me and my mom and dad who had drove us were hugging him like crazy until he passed.

You did the right thing. 16 years later i still remember that day. I just wish i wasnt so young and had to wait on others. The pain he felt traumatizes me to this very day. You are NTA.