Et tu, Brute? is a Latin phrase often translated as "Even you, Brutus?". The quote appears in Act 3 Scene 1 of William Shakespeare's play Julius Caesar, where it is spoken by the Roman dictator Julius Caesar, at the moment of his assassination, to his friend Marcus Junius Brutus, upon recognizing him as one of the assassins. On March 15 (the Ides of March), 44 BC, the historic Caesar was attacked by a group of senators, including Brutus, who was Caesar's friend and protégé. Caesar initially resisted his attackers, but when he saw Brutus, he reportedly responded as he died. Suetonius mentions the quote merely as a rumor, as does Plutarch who also reports that Caesar said nothing, but merely pulled his toga over his head when he saw Brutus among the conspirators.

Source: Wikipedia