This man Jesus, whom you had killed, has been raised and exalted by God as savior of the world so that he can grant you repentance and forgiveness for your sins. Peter and company continue with their bold proclamation of the resurrected Lord. St. Mark the evangelist would now be proud of the transformation that Peter and company had undergone. After three or so years of “not getting it,” the apostles had finally come to get it. There wasn’t anything, not even threats of persecution and death, that was going to muzzle them. They had finally come to understand who Jesus was and what their call was about. Peter had finally come to understand what dying for Jesus really meant. 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 was also suggesting that these men were sinners who were in need of repentance. It was an assertion that didn’t sit well with the audience (the members of the Sanhedrin). 
While those listening to Peter might perhaps have been thinking that Peter was alluding to the particular crime of killing Jesus (of which Jesus had forgiven them already [cf. Luke 23:34]), the repentance and forgiveness of sins to which Peter was referring goes beyond that of the 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 calling 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.