OMG!! How horrible an experience for you and your sweetie. I'm SO sad for you and SO sorry for your deep loss
Agreed that you should take your time to grief in your own way and for ever how long it will take you. There is no specific time frame, as we are all different. Also, agreed that the other dog should be reported asap.
May time relieve the deep pain you are experiencing, and that you will be able to pick up the pieces, one by one, and be able to smile when thinking of all the lovely moments you've shared. That, no one can take from you.
Sending you huge hugs!!!!