Stephen was a great man of God, because he was full of the Holy Spirit. This made the religious leaders so angry, that they took Stephen out and hit him with stones until he died.
Then the Jews began to persecute (beat-up and even kill) many people just because they believed in Jesus as their Savior. This caused many believers to run from Jerusalem and scatter all over the world.
One of the places the believers went to was a city called Antioch. There they started telling everyone (Jews and Gentiles) about Jesus, and people were being saved from their sin.
When Jesus' disciples in Jerusalem heard what was going on in Antioch, they sent a man named Barnabas to check on things. Barnabas was full of the Holy Spirit, and when he saw what was going on in Antioch, he could tell the people were truly being saved. He encouraged them to stay true to God.
Barnabas went to Tarsus and got Paul to come help him preach and teach the new believers. The believers at Antioch were the first to be called Christians.