thinks is right for Rome. And yet here he is, in the middle of a war that he looks certain to lose, unable to properly grieve for the death of his wife.

Subsequently, Brutus demonstrates a philosophical, stoic response to Portia's death, when he says, "We must die," and, "With meditating that she must die once, I have the patience to endure it now." In other words, Brutus appears to accept Portia's death as an inevitable fate that he can do nothing about. He acknowledges that having thought about it before, he has the "patience to endure it now." Of course, in the circumstances, this reaction might be one of pragmatic necessity, rather than a natural reaction. He may appear to react coldly to the death of his wife, but this is because this is the only reaction he will allow himself to have at this time. To react otherwise would be to abdicate his duty and responsibility toward the soldiers that he commands.

Cassius's initial reactions upon hearing of Portia's death are limited to exclamations of surprise, such as "Ha, Portia?" and, "O ye immortal gods!" However, Cassius subsequently admits that if he were in Brutus's place, his "nature could not bear it so." He, perhaps like the audience, is surprised that Brutus can be so stoic and seemingly unemotional in the face of such bad news. This reaction from Cassius is arguably not what an audience might have expected from the Cassius we met at the beginning of the play. The Cassius we first met appeared cold and calculating, whereas the Cassius in act 4, scene 3, seems softer, and more emotionally vulnerable.

In Shakespeare's Julius Caesar's the first reaction of the people of all ranks to the assassination of Caesar is one of terror. Trebonius describes the reaction succinctly when Cassius asks him, "Where is Antony?"

TREBONIUS
Fled to his house, amazed.
Men, wives, and children stare, cry out, and run,
As it were doomsday.

Even the assassins themselves seem confused, shouting contradictory orders, asking questions, wondering what action to take next now that they have created a power vacuum.

Then after Brutus speaks to the plebians in Act 3, Scene 2, the geneeral populace turns against Caesar and accepts the new leadership.

FIRST PLEBIAN
This Caesar was a tyrant.
THIRD PLEBIAN
Nay, that's certain.
We are blessed that Rome is rid of him.

But when Antony speaks to them after Brutus is finished, he slowly brings them around to feeling pity for Caesar and regret at losing him and finally to anger at Brutus, Cassius, and all the other conspirators. The enraged citizens force the conspirators to flee Rome, allowing Antony and Octavius to seize power and begin a bloody purge of all the men they suspect of being in sympathy with Brutus and Cassius.

Order is finally restored in Rome, and Julius Caesar passes into history.

Cassius is upset and surprised when he learns how Portia died, and the audience probably is too.

Portia’s death probably came as a shock to everyone.  Brutus’s wife was a strong woman.  She was Cato’s daughter, and she considered herself a part of her husband’s war effort.  When things did not go well for her husband, it was too much for her.  She took her own life in the most spectacular way.

BRUTUS

Impatient of my absence,
And grief that young Octavius with Mark Antony
Have made themselves so strong:--for with her death
That tidings came;--with this she fell distract,
And, her attendants absent, swallow'd fire.

CASSIUS

And died so?

BRUTUS

Even so.

CASSIUS

O ye immortal gods! (Act 4, Scene 3) 

When Brutus tells Cassius that Portia is dead, it is a reminder that things are not going well for them.  To the audience, it likely seems like everything for Brutus and Cassius’s side is going very poorly.  Portia’s bizarre death may lead the audience to pity Brutus, but Brutus’s reaction to it is a little odd.  He might be in a state of shock or denial. 

He doesn’t want to talk about it anymore.  Cassius tries to bring up the subject again.

CASSIUS

Portia, art thou gone?

BRUTUS

No more, I pray you.
Messala, I have here received letters,
That young Octavius and Mark Antony
Come down upon us with a mighty power,
Bending their expedition toward Philippi. (Act 4, Scene 3)

Cassius may be trying to bring Brutus back down to Earth and help him accept what really happened.  He may he trying to accept it himself.  Shakespeare also might be using this incident as a reminder of how long the war has gone on and how it has affected the families of the men involved.  The war goes poorly for Brutus and Cassius, and it is not about to get any better. 

Based on what Cassius has said about Caesar, we can infer that he will be very satisfied when Caesar is assassinated. Cassius has been the leader of the conspiracy to murder Caesar and has successfully tricked Brutus into joining the plot. Cassius has expressed feelings of hatred and jealousy toward Caesar. He told Brutus stories mocking Caesar as being weak, unfit to rule in Rome. According to Cassius, he even had to save Caesar from drowning on one occasion. Cassius is bitter that Caesar has gained so much power.

Calpurnia will be heartbroken by Caesar's death. She loves her husband and has worried about him a great deal. She has had terrible dreams about his impending death, and all of the strange events in Rome the night before Caesar's murder convinced her that he was in great danger. The morning of the Ides of March, Calpurnia begs Caesar to stay home from the Senate. She uses all of her persuasive powers, but to no avail. Caesar goes to the Senate with the conspirators and is killed. Calpurnia may blame herself for not convincing him to stay home.