I am so sorry for your loss. It is so difficult to lose one of your furry friends suddenly like that.
I have had one dog that had been hit and the guy did stop but it was too late, she was already gone. She was an escape artist and would break free and run. I was not home when it happened but the hubby was. People would fly doing a 100 mph on that road just for fun because when they hit our hill it would make them go airborne. I called the cops numerous times to do something about it because my kids almost got hit several times just getting off of the school bus.
When the guy stopped to ask if this was our dog, all my husband said to him was if that was one of our kids, I would be burying you in the back yard and not the dog because he was most likely speeding.