How the assumption came about.
THE ASSUMPTION OF MARY
Father Clifford Stevens At the Council of Chalcedon in 451, when bishops from throughout the Mediterranean world gathered in Constantinople, Emperor Marcian asked the Patriarch of Jerusalem to bring the relics of Mary to Constantinople to be enshrined in the capitol. The patriarch explained to the emperor that there were no relics of Mary in Jerusalem, that "Mary had died in the presence of the apostles; but her tomb, when opened later . . . was found empty and so the apostles concluded that the body was taken up into heaven."
In the eighth century, St. John Damascene was known for giving sermons at the holy places in Jerusalem. At the Tomb of Mary, he expressed the belief of the Church on the meaning of the feast: "Although the body was duly buried, it did not remain in the state of death, neither was it dissolved by decay. . . . You were transferred to your heavenly home, O Lady, Queen and Mother of God in truth." All the feast days of Mary mark the great mysteries of her life and her part in the work of redemption. The central mystery of her life and person is her divine motherhood, celebrated both at Christmas and a week later (Jan. 1) on the feast of the Solemnity of Mary, Mother of God. The Immaculate Conception (Dec. 8) marks the preparation for that motherhood, so that she had the fullness of grace from the first moment of her existence, completely untouched by sin. Her whole being throbbed with divine life from the very beginning, readying her for the exalted role of mother of the Savior. The Assumption completes God's work in her since it was not fitting that the flesh that had given life to God himself should ever undergo corruption. The prayer for the feast reads: "All-powerful and ever-living God: You raised the sinless Virgin Mary, mother of your Son, body and soul, to the glory of heaven. May we see heaven as our final goal and come to share her glory."
In 1950, in the Apostolic Constitution , Pope Pius XII proclaimed the Assumption of Mary a dogma of the Catholic Church in these words: "The Immaculate Mother of God, the ever-virgin Mary, having completed the course of her earthly life, was assumed body and soul into heaven." With that, an ancient belief became Catholic doctrine and the Assumption was declared a truth revealed by God.
http://www.ewtn.com/library/ANSWERS/AOFMARY.HTM
Revelation 20:6 Blessed and holy are those who have part in the first resurrection. The second death has no power over them, but they will be priests of God and of Christ and will reign with him for a thousand years.
Was John lying and it was really Mary who was the first resurrection?