Have to put down nephew's bulldog

I'm raising my 12yo nephew after his mom (my sister) died from leukemia when he was 7. It was really hard on him. I had been estranged from my sister for years and she reached out and asked me to take him in because she didn't want him to be in foster care. I think I have done a great job raising him. After his mom died, the only thing that he wanted was to take their dog, Axel. He grew up with that dog. Of course, I took the dog too.Axel was essential to my nephew's ability to cope with losing his mother. That dog never left my sister's side when she was sick and didn't leave my nephew's side for the last six years. Axel has been having heart problems and been deteriorating. I spent $4,400.00 last month on vet bills. I've grown attached to Axel, but mainly did it for my nephew. I worked from home all week to stay with him and had to rush him to the vet this morning. The vet told me it was time to put him down.My nephew won't be surprised, but will be shocked and devastated. I've been at the vet's all day with Axel. I don't know if my nephew is going to want to say goodbye or be in the room when he goes down (I will; I want him to see a familiar face as the last thing that he sees). I've been struggling with writing this all day long. I have to pick him up and tell him all of this. via /r/Parenting http://bit.ly/2UWGz0q