What was Saul doing before his conversion?

Answer: Persecuting Christians

Saul was still breathing out murderous threats against the Lord's disciples.

“Meanwhile, Saul was still breathing out murderous threats against the disciples of the Lord. He approached the high priest and requested letters to the synagogues in Damascus, so that if he found any men or women belonging to the Way, he could bring them as prisoners to Jerusalem.”— Acts 9:1-2 (BSB)