I'm sorry you lost your chickens. I know it's hard, but please don't beat yourself up about it. We've lost a lot of chickens due to various causes. We get cold fronts moving in suddenly here, so at this time of year if I forget to check the weather before bed, I accidentally leave baby chicks outside (warm when going to bed) and then wake up to find them dead since the cold front drops the temp by sometimes 30 degrees suddenly when the front hits. I lost 11 babies the other day and felt awful for my mistake. Then another time I learned the lesson of cutting slits into my tarp to let the rain come through when it's a downpour. Earlier the rain puddled on top of the tarp and pressed so hard on the PVC support that it busted and collapsed right onto the pile of chickens below. That time we lost about 8 chicks. Then a few nights ago we lost a turkey to a predator at night. We also recently lost 2 sheep to a coyote.
So just chalk it up to learning something new each time. It is the way most people learn, from personal experience, even though we always think we should be able to learn from other people's mistakes, it rarely seems to work out that way. Plus, it was really the racoon that did the killing, not you!