OK, so I have been planning a book for quite a while now and I'm starting to think about the end. In the last chapter, the protagonist as well his two colleagues discover a twist (it's a crime novel) before approaching the antagonist. One of the colleagues (not the main character) is ahead and confronts the antagonist on a rooftop. They wrestle but the antagonist knocks him off the building, killing him. The main character reaches the rooftops just as this happens and runs at the antagonist in rage before being stabbed by the antagonist. His other colleague and closest friend who already has injuries tries to save him by attacking the antagonist. He is killed but buys the main character some time to pull the antagonist back off the building (where it's assumed he is killed, however it is later revealed he survived). My question is, I know the climax is meant to be a important part of the story where characters could die, but I've (to the readers knowledge) killed off three important characters in a short amount of time and seriously injured the main. Have I done too much damage? Thanks!