That is a very sad story, and I can imagine how disturging it was for you. I hope the person who shook the kitten out of the tree, into the jaws of a waiting hound, has nightmares of guilt. Shame on him! The animal is helpless, and that is a very thoughtless and cruel thing to do.
I once had a friend give me an injured baby rabbit, thinking I would know what to do with it, since I am the "animal girl". It had been mauled by a cat, with sme of it's intesting sticking out of the abdomin wall. I thought it was hopeless and decided to put it out of its misery. Tried to suffocate it in a plastic bag, but it kept coming back to life, or so it seemed. I was doing a horrible job of it, nad ultimately torturing the baby rabbit. Brought it home thinking maybe I could save it, and even thought I'd see if I could put the little loop of intestine back inside, but when my husband saw it he questioned my sanity. When I explained how I had unsuccessfully tried to dispatch it, he said, "give it to me". He went out into the garage and whump! Banged it's head against the wall and killed it cleanly. What I should have done, had I not been afriad of the violence of such a killing. I was so , so upset by that, so reading your story made me remember how bad I felt thinking how I allowed that rabbit to suffer needlessly. Nothing can change that now, and nothing can change your experience either, but don't feel guiltly. You have nothing to feel guilty aobut, least of all having a sweet and soft human heart. I , personally, find that simply endearing about you.