Why does Hamlet kill Polonius in Act 3?

Hamlet actually kills Polonius by mistake. When he hears the noise and movement coming from behind the curtain, he thinks it is his uncle, the king. He has decided he wants to kill the king, as you probably know. So he thrusts his sword into the curtain, thinking he is killing his uncle, and then it turns out to be the wrong person.

Polonius was hiding there spying, so it falls onto him, really. But...

Hamlet actually kills Polonius by mistake. When he hears the noise and movement coming from behind the curtain, he thinks it is his uncle, the king. He has decided he wants to kill the king, as you probably know. So he thrusts his sword into the curtain, thinking he is killing his uncle, and then it turns out to be the wrong person.

Polonius was hiding there spying, so it falls onto him, really. But because of this murder, it triggers Polonius' son to come back to avenge his father's death, leading to the highly dramatic ending of the play.

So to answer your question, he does it because he thinks it's his uncle, the king, hoping to finally get revenge on his uncle for killing his father.

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