I think you did the right thing, and ended it life as best you could.
Frankly I do NOT find the pictures or videos anymore graphic than a snake feeding video, where a rat's life is ended.
Since "graphic" was in the title, there should not have been complaints about content. It states a hawk dropped a bunny and that it's graphic, what else would you expect to see other than a somewhat mauled bunny?
I'm not attacking anyone here, but if you read the title, and think about it, then it seems plain to me. I know people like bunnies, but then people like ratties too. No one seems bothered by feeding pictures or videos. So this should be fine.
Congrats on getting to see a wild hawk too. That must have been cool.