Mercutio and Tybalt started to fight and Romeo was telling them to stop because the Prince said that they couldn't fight.
Tybalt stabs Mercutio under the arm of Romeo and then flies with his followers.
Tybalt returns and Romeo was very upset and challenged Tybalt and then Romeo killed Tybalt.
All the people come out. Then the king ,queen and princess come out to see that Lady Capulet is dead. Then the prince asked Benvolio about what had happened and he said that Romeo had killed Tybalt and that Tybalt had killed Mercutio.
Then the Prince says that Romeo is to banished from Verona.