I'm so sorry this happened to you. I know how excruciatingly upset you were when the cat was killed in your yard too. People risk lives, both their pets' and other people's, when they let their pets run and roam. I have been fortunate enough not to have hit anything myself to this point, but I have witnessed both cats and dogs hit and the images are seared into my heart forever. Sometimes, an animal is out by accident, but all too often it's just people who don't care or don't try to contain them. Where I grew up in Missouri, roaming cats and ferals were practically in epidemic proportions it seemed. Here in MN, I have not seen nearly as many.

The one you hit may have been a feral if it darted out of a field but there's no way to know. Irresponsible pet ownership hurts so many, first and foremost the pet of course, but your case is a perfect example of how much it can hurt others too.