Against whom did Saul begin his rampage after Stephen was martyred?
Saul of Tarsus began his rampage against the believing Jews in Jerusalem, not satisfied with what he had accomplished in Jerusalem and Judea. He then sought to go after the believing Jews at Damascus, acting in the name of religion, thinking he was serving God by stamping out belief in Jesus of Nazareth.
Les explains that the believing Jews at Jerusalem were an Ecclesia, a called-out assembly called out of Judaism, meeting apart but still under Judaism's umbrella, not yet separated from the Law and temple worship. It was against these believing Jews that Saul of Tarsus began his rampage when Stephen was martyred back in chapter 7. Not satisfied with Jerusalem and Judea, Saul wanted to go after the believing Jews up at Damascus. He did all this in the name of religion, thinking he was doing his God a service by stamping out any believing in Jesus of Nazareth.