Short answers, pulled from the story.
Marcus Junius Brutus (c. 85 BC - the 23rd of October 42 BC) was a Roman politician, orator, and the most famous of the assassins of Julius Caesar. He took a leading role in Caesar's assassination on the Ides of March (the 15th of March) 44 BC, and his name has since become a synonym for betrayal in most European languages.
Ancient sources emphasize Brutus's philosophical conviction that Caesar's increasingly monarchical behaviour, including his acceptance of the title dictator perpetuo, threatened the Roman Republic. Brutus was also shaped by his family legacy as a descendant of Lucius Junius Brutus, who expelled Rome's last king. Both the Platonian philosophical tradition and public graffiti comparing him unfavourably to his ancestor appear to have pushed him toward action.
After Caesar's assassination in 44 BC, popular unrest forced Brutus and fellow assassin Cassius to leave Rome. They built armies in the east, but were defeated by Mark Antony and Octavian at the two battles of Philippi in October 42 BC. Following the defeat, Brutus took his own life by falling on his sword.
According to Plutarch, Brutus's last words included "By all means must we fly, but with our hands, not our feet." He also reportedly quoted from Euripides' Medea: "O Zeus, do not forget who has caused all these woes." Ancient sources disagree on whether he was referring to Antony or Octavian with this curse.
Dante placed Brutus in the lowest circle of Hell alongside Cassius and Judas Iscariot, where all three are personally tortured by Satan. Dante interpreted the assassination as Brutus resisting God's historical design for Rome and the eventual fusion of the Roman Empire with Christianity.
The Latin phrase commonly associated with Caesar's death is not recorded in the ancient sources in that form. Cassius Dio reported that Caesar shouted in Greek "kai su teknon" ("You too, child?"), while Suetonius cites a friend of Caesar's, Lucius Cornelius Balbus, as saying Caesar fell in silence. Classicists James Russell and Jeffrey Tatum have noted that "kai su" in Greek also suggests the possibility of a curse rather than a lament.