roger chillingworth stands at the foot of the scaffold how does he explain his presence

He says he was returning from tending to Governor Winthrop when he saw a strange light and camoe over.

I had spent the better part of the night at the bedside of the worshipful Governor Winthrop, doing what my poor skill might to give him ease. He going home to a better world, I, likewise, was on my way homeward, when this strange light shone out