I'm so sorry for your loss. Often times at work when the owner insists on being there when their dog is euth my vet gives them a warning. The dog, even though passed on may have some quick movements, may deficate, gasp for air, or make noises for up to a couple minutes after passing.. The dog is not aware of this. The drug takes effect instantly and the dog has no idea what it's doing.

I'm sorry your experiance was made worse by not having a warning on what to expect.