In Act 1, Scene 2, he is reluctant to join Cassius's conspiracy because he did not want to betray Caesar. He had to weigh his choices and in Act 3, Scene 2, Brutus kills Caesar only because he is afraid of what will happen to Rome if Caesar remains ruler. He knew the commoners’...
he has so much stress on his back from commanding his army and he is pretty sure at this point that the majority of the people he truly cares about are dead. Also after the argument they realize it was just a mistake and Brutus and Cassius both take a drink as a sign of friendship....