I'm proselytizing. You don't have to listen.
When a train stops at a station we don't usually say it has passed from motion to motionless. We don't tend to think of stopping as a transition.
What things stop? A song. I might say the song stopped, or the song was over, but I don't generally say the song passed.
A bullet entering a cat's skull eventually stops. We don't say the bullet passed. When the beating of the cat's heart stops… it stops. It doesn't pass because there's nothing for it to pass to. Actions don't pass into inaction, they simply stop acting.
And so when the cat's heart stopped, when his consciousness stopped, his consideration for his sister, his insistent desire to be petted, his creature presence as a member of this family stopped, I don't say he passed. I say he died. He stopped being.
What did pass? My dread passed to grief. The dread of what I was about to do, the dread of how his life would stop passed to a state I can only describe as 'out of heart' -- when I picked up the rifle like an automaton and told myself, "Do it." The one shot was enough but as I'd planned I fired a second time according to a script, that, once set in motion, I couldn't stop. But with that, the script ended and my feelings flooded back in overwhelming shock. The shock at having so suddenly lost a dear friend, a brother. I sat and put my head in my hands. And the shock passed into sobs of grief.
I returned to the cat's body. My knowledge that this cat had died, had not passed but stopped, did not keep me from resting my hand on his stomach and saying goodbye as if there was a cat to say goodbye to, as if it was the same cat who, every time I let him in would mrrow with closed mouth and I would say, "You're welcome."
Yes that cat. That cat is dead.
When will my grief pass into a wistful regret, a poignant memory? Or perhaps it will transform into a cold resentment at the finality of death. Or perhaps there will always be a touch of grief until I stop.