‘But Mary was standing outside at the tomb weeping, so as she wept she stooped and looked into the tomb, and she sees two angels in white, sitting one at the head and one at the feet where the body of Jesus had lain.'
Mary must have followed the other two, returning back more slowly. She could not keep up with the intense running of the men, especially as she had already had the journey the other way in order to tell them. She would thus arrive back after the two had left. They, of course, had left her standing, not thinking of whether she would follow.
Still distraught, tears were pouring from her eyes. It was the custom in those days to let grief have its full sway and she may well have been weeping loudly and vigorously as the verb suggests. Deeply distressed she bent to look into the tomb. And then she froze in amazement. For there she saw two figures in white sitting where the body had been lying.
The angels may have been seated as being temporary protectors of the place where Jesus had lain, just as the Cherubim had been protectors of the Ark. Or more likely (they had not been there when John and Peter arrived) they may have wished to draw attention to the exact spot where Jesus' body had been (none of His followers would otherwise have known at which spot His body had been placed). They may also have been present as an indication to all who saw that Jesus had been escorted by angels into God's presence. This would be in accordance with Luke 16:22 which seemingly reflects Jewish tradition.