Hamlet loved Ophelia, then he hated Laertes because he jumped into the grave with Hamlet. This made both Hamlet and Laertes mad at each other.
Act 5 Scene 2
Hamlet and Laertes fight they both end up died, but before this happens the Queen dies from poison met for Hamlet, before Hamlet dies he kills the king. Horatio was going to drink the poison but Hamlet tells him not to so that he could the story of had happened.