"I say the murderer of the man whose murder you pursue is you"
Oedipus' hamartia is his temper. He is quick to anger, which leads him to make impulsive decisions, like hurting the Shepherd or threatening Tiresias, which is the beginning of his downfall.
"Lost! Ah lost! At last it's blazing clear!"
Oedipus' excessive pride causes him to promise the people of Thebes that he will catch and punish Laius' murderer. He also is quick to dismiss ideas that aren't his own.
Events begin to turn against Oedipus when Tiresias accuses him of killing Laius. Tiresias is blind, but is a seer, so he sees the truth. However, Oedipus does not believe him.
When Oedipus realizes he is the murderer and that the prophecy has come true, he has reached anagnorisis. Even though he could physically see, he was blind to the truth.
Oedipus' downfall is when his wife and mother, Jocasta, kills herself. He is further punished when he pokes out his eyes with the pin from her dress.
When Oedipus stabs out his eyes and begs Creon to banish him to Cithaeron, the chorus pities him. This in turn makes the audience feel sorry for Oedipus, despite the fact that he brought it upon himself by searching for the truth.