Complex sentence: The disciple knew then that this was no ordinary monk, but the Archangel Gabriel, and the angel disappeared, and the icon of the Mother of God continued to radiate light for some time afterward.
Split into simpler sentences: The disciple knew then that this was no ordinary monk, but the Archangel Gabriel. At that moment and the angel disappeared, but the icon of the Mother of God continued to radiate light for some time afterward.