Answer:
Hamlet is shocked because Claudius's reaction to the play clearly shows his guilt.
Explanation:
According to the excerpt from Hamlet, Hamlet cleverly stages a play that shows a brother killing his brother to take the throne, to mirror the actions of his uncle Claudius on his quest to become king.
During the course of the play, King Claudius becomes uncomfortable and leaves the play and Hamlet is shocked because he was not sure the ghost's accusations were true but now it has been proven beyond all doubt.
