I accidentally killed a bobtail lizard once, and I cried for about an hour afterwards. He shot straight out infront of my car and I braked, but he got caught by one of the tires. I love lizards, and most wildlife and hate that I ran it over. Living in Australia I know a few people who have had accidents involving kangaroos; I think that would break my heart.
A kookaburra flew straight into out 4WD's protector windscreen wire mesh. We were driving to our regular campsite up-scrub.
We stopped to check, & his neck was broken.
My husband decapitated him with our very sharp axe, to end the poor little bird's pain. It's the only humane action we could do.
We buried him by the roadside.
Every time we passed that 'spot', we said a little prayer for him.
It really upset us, for a long time, as we both love animals', of any description.
On a good note, I found a Tawny Frogmouth Owl, on the side of a road. I think he'd been hit by a car, so I gingerly took him home, put him in an air-holed shoe box, with heaps of soft tissues for him to lie on, & called our local 'bird-man'.
He took him to nurse him back to health, as he said the little owl had a broken wing. Once healthy enough, he would take him back into the bush, to be released.