Saul 

Saul is said to be a Hebrew name.

Saul is said to have been the name used by Paul when he was persecuting Christians before becoming one of the disciples of Jesus Christ when he is said to have been struck blind on the road to Damascus.

Saul is said to have been a Diaspora Jew from the southern Turkish city of Tarsus.

He seems to have changed his name to Paul when a young man when he became a Roman citizen.

It seems impossible that he could have been going after Christians at this time since the Christian Church did not yet exist.  Christianity did not develop until well after the death of Jesus Christ. (See "The Second Messiah" p3)