Supposedly the last words of Julius Caesar. Literally 'And you, Brutus?' / 'Even you, Brutus?' (III, i, 77)
Caesar: Doth not Brutus bootless kneel?
Casca: Speak, hands, for me! [They stab Caesar.]
Caesar: Et tu, Brute? Then fall, Caesar! [Dies.]
Cinna: Liberty! Freedom! Tyranny is dead!
Today "Et tu, Brute?" is known as a expression describing betrayal and assassination.