Acts 7 Authorized (King James) Version (AKJV)
54 When they heard these things, they were cut to the heart, and they gnashed on him with their teeth. 55 But he, being full of the Holy Ghost, looked up stedfastly into heaven, and saw the glory of God, and Jesus standing on the right hand of God, 56 and said, Behold, I see the heavens opened, and the Son of man standing on the right hand of God.
It would be interesting to know the extent to which Stephen saw God the Father while this stoning was taking place.