St Peter, the brother of St Andrew, was a fisherman on the sea of Galilee. He was married, and Christ healed his mother-in-law of a fever (Mt.8:14). He, with James and John, witnessed the most important miracles of the Savior's earthly life. Despite his earlier recognition of Christ as the Son of God, he denied Him three times on the night before the Crucifixion. Therefore, after His Resurrection, the Lord asked Peter three times if he loved Him. Then He told Peter to feed His sheep (John 21:15-17). After the descent of the Holy Spirit at Pentecost, St Peter addressed the crowd (Acts 2:14), and performed many miracles in Christ's name. He baptized Cornelius, the first Gentile convert (Acts 10:48). He was cast into prison, but escaped with the help of an angel (Acts 5:19). St Peter also traveled to many places in order to proclaim the Gospel message. He wrote two Epistles, which are part of the New Testament. St Peter was put to death in Rome during the reign of Nero. According to Tradition, he asked to be crucified upside down, since he did not feel worthy to die in the same manner as his Lord.
Crucifixion of St. Peter - by Caravaggio