Brutus wants the assassination to be a sacrifice, not a butchery (2.1). What is being sacrificed? How would you describe the attack on Caesar?

Brutus warns against a bloodbath; he does not want Caesar's murder to be barbaric..... he wants the assassins to look thoughtful. The attack on Caesar is anything but what Brutus intended. It is, in fact a butchery committed in the throes of blood lust.