Each Gospel records an account of Jesus' resurrection in similar terms.
The Gospel of Matthew explains how Mary Magdalene went to see the tomb:
After the sabbath, as the first day of the week was dawning, Mary Magdalene and the other Mary came to see the tomb. And behold, there was a great earthquake; for an angel of the Lord descended from heaven, approached, rolled back the stone, and sat upon it. His appearance was like lightning and his clothing was white as snow. The guards were shaken with fear of him and became like dead men. Then the angel said to the women in reply, “Do not be afraid! I know that you are seeking Jesus the crucified. He is not here, for he has been raised just as he said. Come and see the place where he lay. Then go quickly and tell his disciples, ‘He has been raised from the dead, and he is going before you to Galilee; there you will see him.’ Behold, I have told you.”
The Gospel of John is much shorter in its account and simply states, " On the first day of the week, Mary of Magdala came to the tomb early in the morning, while it was still dark, and saw the stone removed from the tomb." (John 20:1)
In all of the accounts, Mary Magdalene only sees the "empty tomb." While it is true that she does see a miraculous appearance of an angel, she does not see the resurrection happen.
The Catechism of the Catholic Church affirms this reality:
O truly blessed Night, sings the Exultet of the Easter Vigil, which alone deserved to know the time and the hour when Christ rose from the realm of the dead! But no one was an eyewitness to Christ's Resurrection and no evangelist describes it. No one can say how it came about physically. Still less was its innermost essence, his passing over to another life, perceptible to the senses. Although the Resurrection was an historical event that could be verified by the sign of the empty tomb and by the reality of the apostles' encounters with the risen Christ, still it remains at the very heart of the mystery of faith as something that transcends and surpasses history.
The resurrection of Jesus happened at some point before Mary Magdalene arrived at the tomb.
By the time she arrived, Jesus was already risen and no longer lying on the stone slab inside the tomb.
In reality, the only other beings who saw Jesus' resurrection take place were the angels.
They were there the whole time and were present with Jesus inside the tomb, as well as in Heaven.
