Paul was a good Jew and persecuted the followers of Jesus because he was zealous for God and felt that these Jews who were folloing the teachings of Jesus were not being faithful Jews. It took a great light from the sky and a voice that said, "Saul, Saul, why are you persecuting me?" Paul asks who is speaking with him and he hears Jesus say: "I am Jesus the Nazorean whom you are persecuting." Paul asks what is he to do and Jesus tells him: "Get up and go into Damascus and there you will be told about everything appointed for you to do." Since Paul could not see because of the brightness of the light, he was led by hand into Damascus.
This is a dramatic conversion story and Paul will become the Apostle who will convert so many to follow Christ. I love to go back and read the Acts of the Apostles to follow both Peter and Paul as they went about teaching others and converting them to also be followers of Christ.