it could have been residual nerve impulses. but either way when an animal is just mindlessly moving it's limbs, it's usually just a matter of time, or it's already gone. I sympathize with your feelings in this. I have been placed in the same situation before. it isn't an easy call...what do you do? I can be pretty sterile and clinical at times, but I find as more time passes since I have left the military & law enforcement life, or maybe it's because I'm just getting older, that I'm realizing a little more sensitivity on things such as this. I could not have just smashed it's head with a rock or something, but who carries a syringe of anesthesia around... you know? there have been a few times when the animal expires in the few seconds when I'm still pondering what to do. I have to say it was a relief when I didn't have to make the choice.
about 6 years ago, a past girlfreind of mine had 2 young children; a boy (2) and a girl (4). we frequently would take them for a good drive at night to put them to sleep. one night in particular, we were just about to get on the highway from the frontage road after I had taken them down "roller coaster hill" ( so named because if you went over these 3 closely spaced hills at a good clip you would feel significant & -
G's ). just before the on-ramp a racoon darted into the road.
I couldn't do anything and hit it. I stopped and went to check on it, taking my duty sidearm. it was already dead, no breathing, no movement. the children figured out what happened and of couse were upset. the boy was particularly sensitive and was crying. ( he bawled once when, while trying to pin a "cow ant" with a twig, to show it to him, I accidentally severed it's thorax ). their mother told them the racoon would be ok...I didn't know what to say. I figured I would tell them the truth and try to comfort them, but they seemed to calm and after about 20 min in the drive they had settled.
on the return trip back from the next town I took a different country 2 lane highway. about 5 miles outside town I hadn't gotten up to the 65 speed limit yet...another racoon leaped into the road. I braked hard as possible without drifting into the opposite lane or endangering us & the kids more than necessary. I HIT THIS ONE "TWO"...I almost stopped in time but it darted into in the tires as it tried to run back. it was closeby and I could tell it was still alive, struggling to make it back to the woods. the kids by this time were traumatized, both crying. the little girl gave me such a pitiful look as to convey the question that I had brought them out to some sick sporting event! I got out...again...with my weapon. the animal had collapsed a few feet away and was lying outstretched laboring hard to breathe. I waited a moment, pondering...and waiting for the mother to distract her children from the sight...then fired center-mass to make it clean. I sighed and paused a moment before getting back to the truck...struggling to stay in the "flat affect" of logic. when I got in my girlfriend was sobbing, the kids were sobbing, and I couldn't hold up. I silently gave it the few tears I guess I felt I could allow on the drive back. I would have buried it but I had nothing to dig with. had the children not been asleep again by the time we returned, I would have driven the 20 miles back to do so. but we felt the situation best that we let them sleep and try to get them over it the next day. it took a bit of reassuring too, in the following days, just to convince them I wasn't hunting racoon with the truck...
you might take some comfort in the likelyhood that it was probably too deep in shock to feel anything, or it was already dead and what you saw was the neuromuscular response as the brain's last bit of current drained away.
anyway, I thought if I shared that horrible event you'd be so shocked by the end you'd forget what it was you asked me about...
Mick