What is the mood in Act 3 Scene 1 of Romeo and Juliet?

Whenever we think about mood we are actually talking about
the feeling or atmosphere that a given story evokes. Thus a horror story could evoke a
mood of fear and trepidation, or a story about nature in the countryside could evoke a
mood of peace and tranquility. The important thing is to consider what happens and then
to think about what emotional feeling it has on you. When we consider Act III scene 1 of
this excellent tragedy, we can see that there are two distinct moods. There is one of
lighthearted humour that accompanies the banter between Mercutio and Romeo as they
engage in their verbal battle of wits, and then there is a much darker, suspenseful mood
as Tybalt kills Mercutio and is then killed by Romeo, concluding in the Prince's exiling
of Romeo:

Let
Romeo hence in haste,

Else, when he is found, that hour is
his last.

Bear hence this body and attend our
will.

Mercy but murders, pardoning those that
kill.

Note the way in which
Romeo's grief and rage against his situation is captured in his line, "O, I am fortune's
fool!" The mood has changed distinctly from the easy, light-hearted one at the beginning
of the scene to one of tragedy, as Romeo has been forced to kill Juliet's kinsman, who
is actually now his kinsman now that he has married Juliet.