When the Jews killed Jesus, they did not believe they were sinning. They thought they were doing God a service. In his ignorance, the apostle Paul was guilty of hailing of men and women into prison, and very likely, people were persecuted and maybe even some were put to death. In regard to the death of Stephen, the indication is that Paul was a ringleader in it. He thought he was doing God service, a favor, but when he was stopped by the light of God on the road to Damascus, and the truth was suddenly revealed to him, he realized he was nothing but a hunk of junk lying blind on the road.
The Holy Spirit did that. It smote these people in the heart so that they could clearly see that they were individually responsible for the death of Jesus Christ, even if they had not been there when it actually took place.
Without the Spirit of God, the truth of God is like looking into the gloom. We see the shape and form of things, but without the Spirit of God, the truths—the doctrines, the teachings—that make up the mechanism of God's purpose do not make sense. They cannot be put in their right order so that they really add up or give a clear picture of what God is doing.
John W. Ritenbaugh
Truth (Part 3)