Now when they heard these things they were enraged, and they ground their teeth against him. But he, full of the Holy Spirit, gazed into heaven and saw the glory of God, and Jesus standing at the right hand of God; and he said, “Behold, I see the heavens opened, and the Son of man standing at the right hand of God.” But they cried out with a loud voice and stopped their ears and rushed together upon him. Then they cast him out of the city and stoned him; and the witnesses laid down their garments at the feet of a young man named Saul. And as they were stoning Stephen, he prayed, “Lord Jesus, receive my spirit.” And he knelt down and cried with a loud voice, “Lord, do not hold this sin against them.” And when he had said this, he fell asleep. And Saul was consenting to his death. (Acts 7:54-8:1)This is a slightly expanded version of the end of the readings today. Saul would later be known as Paul, of course, after receiving his own visit from the Risen Lord.
Who was Stephen? He is known from Acts as one of the first seven deacons of the church. The Bible offers no information regarding his life before his ordination.
Stephen's life previous to this appointment remains for us almost entirely in the dark. His name is Greek and suggests he was a Hellenist, i.e., one of those Jews who had been born in some foreign land and whose native tongue was Greek; however, according to a fifth century tradition, the name Stephanos was only a Greek equivalent for the Aramaic Kelil (Syr. kelila, crown), which may be the protomartyr's original name and was inscribed on a slab found in his tomb. It seems that Stephen was not a proselyte, for the fact that Nicolas is the only one of the seven designated as such makes it almost certain that the others were Jews by birth. That Stephen was a pupil of Gamaliel is sometimes inferred from his able defence before the Sanhedrin; but this has not been proved. Neither do we know when and in what circumstances he became a Christian; it is doubtful whether the statement of St. Epiphanius (Haer., xx, 4) numbering Stephen among the seventy disciples is deserving of any credence. His ministry as deacon appears to have been mostly among the Hellenist converts with whom the Apostles were at first less familiar; and the fact that the opposition he met with sprang up in the synagogues of the "Libertines" (probably the children of Jews taken captive to Rome by Pompey in 63 B.C. and freed hence the name Libertini), and "of the Cyrenians, and of the Alexandrians, and of them that were of Cilicia and Asia" shows that he usually preached among the Hellenist Jews. That he was pre eminently fitted for that work, his abilities and character, which the author of the Acts dwells upon so fervently, are the best indication. The Church had, by selecting him for a deacon, publicly acknowledged him as a man "of good reputation, full of the Holy Ghost and wisdom" (Acts 6:3). He was "a man full of faith, and of the Holy Ghost" (vi, 5), "full of grace and fortitude" (vi, 8); his uncommon oratorical powers and unimpeachable logic no one was able to resist, so much so that to his arguments replete with the Divine energy of the Scriptural authorities God added the weight of "great wonders and signs" (vi, 8). Great as was the efficacy of "the wisdom and the spirit that spoke" (vi, 10), still it could not bend the minds of the unwilling; to these the forceful preacher was fatally soon to become an enemy.This is from the Catholic Encyclopedia. You cant find more information about St Stephen there.