On the way to Caesarea Philippi what remarkable discovery was made by Peter?

Matthew: “He [Jesus] asked his disciples, saying, Whom do men say that I the Son of Man am? And they said, Some say that thou art John the Baptist: some Elias; and others, Jeremias, or one of the prophets. He saith unto them, But whom say ye that I am? And Simon Peter answered and said, Thou art the Christ, the Son of the living God. And Jesus answered and said unto him, Blessed art thou, Simon Bar-jona; for flesh and blood hath not revealed it unto thee, but my Father which is in heaven” (xvi, 13–17).

According to Matthew, Jesus is astonished at the discovery of Peter and attributes it to a revelation from Heaven. Yet previous to this, and in the presence of Peter, according to the same writer, the other disciples had declared him to be “the Son of God” (Matthew xiv, 33).