The very first thing that happen was that Tieresias told the King and Queen that their future son will kill his father (the king) and marry his mother (the queen)
My son will kill me?
Since the parents did not want that to happen, they tied their sons ankles together and left him on the top of the hill to die, but instead he was found by the herdsman and was adopted.
Now the prophecy shall never come true!
Some time pass and Oedipus is told that he will kill his father, not knowing that the man his living with is not his real father, he flees from his house and town so he will not hurt who he thinks is his father. In the way from running away, he is met with the king and his men at a crossroad and killed all the men and the king. Just one of the servants escaping
What! I am not going to be the cause of my fathers death! I shall never let that occur!
I will take revenge for our last king! I will make sure his killer suffers!
After Oedipus has killed the king, who is his real father, he marries the queen, who is his mother, but he doesn't know that. Later every one is getting ill in the kingdom, and the women aren't able to have kids. They ask Apollo for help and learned that the murder of the king is still roaming around the streets and all the misfortune will be gone after they find the murder and take revenge.
They ask the herdsman that works in the kingdom what he remembers and he then reveals that he had saved Oedipus from the hill and gave him a real life. From their Oedipus and and the Queen, who he now knows is his mother realize that Oedipus had actually killed his father and married his mother. Tieresias was right
I saved you that day....who you were living with adopted you, you are not their real son, the king was your father
After the realization that The queen had married her own son, she went in the room and hung her self. After Oedipus saw her he was full of regret and repeatedly stabbed his eyes with her jewelry she wore. Later he asked his brother in-law to take him away and take care of his daughters for him.
It was actually true.... my son killed his own father and married me, his mother!