Peter and John saw the empty tomb of Jesus, yet, they did not believe that He had been resurrected, but John himself later wrote,
“For as yet they did not know the Scripture, that He must rise again from the dead” (John 20:9).
One such passage that they knew was Psalm 16, but they did not necessarily understand that it spoke of the resurrection of the Messiah. Have you read passages in the Bible, but not understood them, and then later something happens that causes you to understand it? Therefore, when they heard a report that the body of Jesus was not in the tomb, they did not immediately conclude that He had been raised from the dead in fulfillment of prophecy.
Yet, when they did finally see the fullness of the truth, they, along with the other apostles, changed the world forever. How has the resurrection of Jesus Christ affected you?