He thought he was killing Claudius.
When he killed Polonius he thought he was killing Claudius. Everyone else he killed, he killed on purpose.
Hamlet killed Polonius when he asumed Claudius was hidding behind the curtain when it was actually Polonius.
hamlet killed polonius by accident. polonius was hiding behind the arrays in gertrudes room and hamlet thought it was claudius so he stabbed him with his sword only to find that it wasnt cladius, but polonius.
Before Hamlet enters his mother's chamber, Polonius is having a discussion with Hamlet's mother Gertrude. As Hamlet enters the room, Polonius conceals himself behind a tapestry hanging from the wall. When he hears Gertrude begin to feel threatened by Hamlet, he cries out for help, thinking that he would kill them both. Hamlet hears Polonius, and believes him to be a rat/spy (possibly even King Claudius, but it is unclear if he truly believes this). Hamlet stabs through the tapestry killing Polonius, who remarks "O, I am slain".
Hamlet stabbed him right behind the arras in Queen Gertrude's room.
hamlet killed king Claudius, Polonius, and laertes. (he technically killed rosencrantz & guildenstern because of a letter telling the king of England to kill them)
Polonius is killed when Hamlet is arguing with his mother Gertrude and Polonius is hiding behind an arras. When his mother calls for help, he also calls and Hamlet stabs him through the arras beliving that it is Claudius hiding behind it. Rosencrantz and Guildenstern are recruited by Claudius after Hamlet kills Polonius to escort Hamlet to England along with a letter for the King of England to have him killed. Hamlet finds and rewrites the letter instructing them to be killed instead. Their ship is attacked and Hamlet returns to England leaving them to go to their deaths in England. Ohphelia, Hamlet's girlfriend, commits suicide when she discovers that Hamlet killed her father Polonius. Gertrude drinks from a poisoned cup that Claudius had prepared for Hamlet to kill him. Laertes takes part in a duel with Hamlet and scratches him with a poisoned sword - poisoned by Claudius. However, later in the duel the swords are switched and Hamlet stabs Laertes with the poisoned sword, killing him. Claudius is forced to drink poison by Hamlet for revenge of killing both his mother and father. Hamlet dies after being scratched by the poisoned sword.
Claudius does not ask Hamlet what he has done with Polonius, although Rosencrantz and Guildenstern do. He asks Hamlet where Polonius is. His lines are "Now, Hamlet, where's Polonius?" and "Where is Polonius?". Hamlet answers, first that Polonius is at supper (not where he eats but where he is eaten) and second that Polonius is in heaven (where Claudius cannot go to find him). Then he adds, "But if indeed you find him not within this month you shall nose him as you go up the stairs into the lobby."
I think he was afraid Hamlet was going to find out that Claudius killed Hamlet's father.
Polonius didn't have any type of cover or guard while listening in on the conversation and wasn't expecting for Hamlet to notice him, "him"(What Hamlet had thought was the supposed Claudius) It was maybe because Hamlet had thought Polonius was Claudius, but even so. Polonius hid behind the tapestry or the arras while he was eavesdropping on Gertude and Hamlet. Hamlet thought that it happened to be the king Claudius who was spying on him and had hid behind there, but to his unknowing, after slashing away at the cloth he found that he had killed Polonius. Hamlet, instead of being shocked by killing the man said that he was a fool and hid his body somewhere.
Hamlet says, "But, indeed, if you find him not within this month, you shall nose him as you go up the stairs into the lobby."
Ophelia's father is Polonius, who is Claudius' advisor. Polonius is killed by Hamlet when he is hiding behind a tapestry, spying on Hamlet as he talks to his mother, Gertrude. After Polonius' death, Ophelia goes mad and eventually dies after she falls from a tree into a brook and drowns.