At the beginning of the play, Romeo has been unsuccessfully trying to engage the affections of a girl called Rosaline. He is playing the part of the rejected lover, staying in his room, moping, and not talking to his friends.
Romeo's father is worried about him because he has noticed that Romeo has been acting strangely by isolating himself in his room, wandering aimlessly, and not eating or sleeping well. Romeo's behavior has become a cause for concern for his father.
He is challenging Romeo to a duel. As Mercutio says, "A challenge, on my life."
Because he thinks Juliet is dead.
They think she is sad because Tybalt is dead. In fact she is sad because Romeo is banished. Her mother tries to cheer her up by saying that she will have Romeo assassinated.
He had already indicated the sad conclusion of the play in the title: The Lamentable Tragedy of Romeo and Juliet.
Romeo and Juliet is a tragedy. They both kill themselves.
Romeo and Juliet by Shakespeare
It is sad but sweet if that is what you mean.
That her and Romeo could not be together.
Romeo is sad in Scene 1 act 1 because he is in love with Rosaline but she doesn't love him back.
because Juliet didnt love him
Read it. It is very sad.