How does the song "apologize" relate to brutus?

ok so im uming u have read the book The tradgedy of Julius Caesar. well in this story Brutus is his best friend but joins with a group of conspirators to kill Caesar. in the end he delt the final blow killing his best friend and Caesar's final words are famous in greek but i cant remember em. something like and u too Brutus. at this moment Brutus realizes what a terrible mistke he made but its "too late to apologize" because his friend is already dead. hope it helps