A civil war breaks out after Caesar is assassinated. Brutus is now fleeing for his life. Because of Antony's speech, the people are rallied against Brutus and the conspirators.
Brutus has lost his freedom afterall. He also loses his beloved wife Portia. Life for Brutus has become unbearable. The irony is that Caesar still haunts Brutus. He is not rid of him despite the bloodshed.
Caesar lives on in the form of a ghost. Brutus sees him and hears him.
Now Brutus, the honorable Brutus, is considered a cold blooded murderer. The people have turned against him. He has lost his authority and the people no longer respect the honorable Brutus.
Now Brutus is living his life running from the people who once loved and respected him.
While Brutus may even question his own part in the assassination, as to whether or not it was the right thing to do, he can be reassured in the last words of Caesar. "Et tu, Brute? Then fall Caesar." Even Caesar is convinced that he should die because Brutus took part in the assassination. Caesar's last words indicated that he respected Brutus in his decision. When Caesar realizes that Brutus is a part of the conspiracy, he determines that he should fall.