What does Acts 3:18 mean?

Peter has been talking about the responsibility of his Jewish audience in Jesus' crucifixion. Details of that crucifixion are scattered all over the Old Testament:

• In Psalm 22:16, "dogs" encompass the victim and evildoers "pierce" his hands and feet. "Dog" was a derogatory term for a Gentile; it was the Roman governor Pilate who ordered Jesus' death and the Roman guards who saw it done (Matthew 27:26–31).
• In Psalm 41:9, David talks about a close friend who lifted his heel against him. Of course, it was Judas who betrayed Jesus (Mark 14:10).
• The "Suffering Servant" passage (Isaiah 52:13–53:12) has many prophecies about Jesus. Isaiah 53:7 talks about His silence in the face of affliction. It is true that Jesus answered questions (Mark 14:62; John 18:20–23, 34–37) but He never spoke in His own defense.
• The words that Jesus spoke on the cross (Matthew 27:46) were originally found in Psalm 22:1.
• David also prophesied the insults Jesus received on the cross (Matthew 27:41–43) in Psalm 22:7–8, including the very specific, "He trusts in the LORD; let him deliver him."
• Psalm 22 also predicts that Jesus' clothes will be divided by lots (Psalm 22:18), which the soldiers did (John 19:23).

Some critics claim that when Matthew, Mark, Luke, and John wrote their Gospels, they twisted details in their accounts to match Old Testament prophecy. But Matthew, Mark, and Luke wrote within thirty years of Jesus' crucifixion. If they included any discrepancies, or points not widely accepted by Christians at that time, there were plenty of eye-witnesses still alive who would have contradicted their stories. Truly, God gave David and the other prophets specific things to include in their writing. Those details were given so it can be clear to us that Jesus is the Messiah, just as it was to the two disciples on the road to Emmaus (Luke 24:13–35).