What is it ironic that oedipus curses Laius murderer

In Oedipus the King, it is ironic that he curses Laius' murderer because Oedipus is actually his murderer. We find out that while traveling to the city where he is now the king, he murdered a man during an argument on the streets. This man ends up being Laius, although Oedipus did not know this at the time.