"Hmm... looks like the people of Rome want me to overthrow Caesar.
Before the whole plot of Julius Caesar, Caesar and his army defeat and kill Pompeii. Caesar now becomes the leader of Rome.
In Act 1, Cassius is trying to manipulate Brutus into rebelling against Caesar.
"You're no good, Brutus!"
"Cassius, you greedy fool!"
Cassius had earlier planted fake letters in Brutus' study that lie about how the people of Rome want Brutus to overthrow Caesar and want Brutus to be king.
"... I see that Brutus has killed himself."
Brutus, Cassius, and all of the other rebellers falsely trick Caesar into thinking they like him, but then, unexpectedly, they all stab Caesar and kill him.
Brutus and Cassius have a big argument, but afterwards, they made up and became good friends again.
Antony finds out that Brutus killed himself, and Antony's army declares victory over the battle between them and Brutus' army. Antony says that Brutus is honorable and that he loved Rome, so he should be buried properly.