Read Acts 26:9-19, then reread it, letting it play as a movie in your mind. Drop yourself down in the middle of the action. Feel the heat of the sun. Smell the horse dung. Cough at the dust raised by the long entourage that accompanied Saul. See the bright flash of pure Light that turns the sun into shadow. Hear the resonant voice of Jesus speak to a suddenly blind, prostrate enforcer.
Saul was sincere and passionate about serving God. To the best of his ability, he obeyed every law he knew--both those which YHWH had commanded and those contrived by generations of Jewish clergy. Ignoring the wisdom of his beloved teacher Gamaliel (Acts 5:33-39), Saul made it his mission in life to stop the people of The Way, Christians, in any way and by all means at his disposal. He rounded them up and cast them into prisons only until they could be killed. Men, women, children, infants--it mattered not to him. These people had to be stopped! If they tried to escape from the persecution into distant cities, he tracked them down. His reputation spread far, so that believers would quake at the name of Saul of Tarsus, a murderer. And all in the Name of YHWH.
But YHWH had other plans for Saul, to be renamed Paul. Those plans were in place before the foundation of the world was laid. First on the list was to get Saul's attention, which our Lord did dramatically on the Damascus road, as you just read. Did Saul believe then? You betcha! Did his direction in life do a 180? Absolutely! Read all of his letters in the New Testament, if you need evidence of that.
Saul, in his sincere efforts to be good was murderously wicked. Trying to be right, he was totally wrong. Notice that Saul wasn't seeking God on the road to Damascus. Why should he? He had God all figured out. He had God in his back pocket. God was on his side cheering him on. Or so he thought until Sovereign God, Holy God, Creator of the Universe, came after Saul, slam-dunking him into the dust.
Was a serial murderer saved that day? You betcha! Is there hope for you, considering all you've done to violate God's law? Absolutely! Paul's story encourages me greatly. If He can forgive a man like Saul of Tarsus, who stood and gleefully watched the stoning of the young deacon, Stephen, cheering on the self-righteous crowd; who signed the death warrants of untold numbers of believers, who masterminded attempted genocide against followers of The Way, He can forgive me. And you. If you haven't done so already, repent and be saved.