This man Jesus, whom you had killed, has been raised and exalted by God as savior of the world to grant you repentance and forgiveness of your sins. Peter and company continue with their bold proclamation of the resurrected Lord. Mark the evangelist would now be proud of Peter and company. After three or so years of “not getting it,” they have finally come to get it. Nothing, not even threats of persecution and death, would muzzle the apostles for they have come to understand who Jesus is and what their call is about. Peter has finally come to understand what dying for Jesus really means. And although his message, just like that of Jesus, was not being received well by those to whom he was preaching (the Sanhedrin), he didn’t budge from speaking his mind even as he proclaimed the risen Christ. In addition to  wanting to bring Jesus’ blood upon their heads, Peter is also suggesting that they are sinners who are in need of repentance. It was an  allegation that didn’t sit well with the audience (the members of the Sanhedrin). 
While those listening to Peter might have had in their mind the sin of killing Jesus (of which Jesus had forgiven them already [cf. Luke 23:34]), the repentance and forgiveness of sins that Peter refers to goes beyond that of killing Jesus. For Peter was referencing the “bigger” sin that led to the killing of Jesus:  humanity’s collective sin. The death of Jesus was occasioned by persistent rebellion by men and women against the commands of God. Jesus was killed because he was calling men and women to a responsible living of their call as co-creators with God. Jesus was killed because men and women had become indifferent to the needs of the other. It was not only to the members of the Sanhedrin that Peter was preaching repentance. Rather, he was calling upon the human race to repent and ask for forgiveness for failing to live up to their call of being the image and likeness of God. For it is this that took Jesus to the cross. And as long as we continue to rebel against the commands of God, we too share in the guilt of killing Jesus.