My Best Friend Is Dead What Now?

I don't really know how to describe whats happening  to me. Overwhelming grief , extreme guilt and disbelief . My 13 yr old Maine Coon "Boots"

 was killed by a local Veterinarian that gave him a shot of poison {Depomedrol.} I had my "Boots" cremated  and it came time to pick him up a few days ago. I keep looking at this fucking box and thinking ...WHERE IS MY LITTLE FRIEND-ARE THESE REALLY HIS ASHES IN THIS BOX...REALLY?. NO...
I can honestly say that I hate that Veterinarian.He devastated me. Boots was all the family I had left. I am so very sorry my Sweet Little Boy...