BOSTON (CBS) – A 9-year-old boy was seriously hurt while skiing at Nashoba Valley in Westford Sunday.

The boy was skiing with his father and when the father reached the bottom of the hill, he turned around and found that his son was not with him.

The father went back and found his son unconscious in the woods, still wearing a helmet.

He had apparently gone off the trail.  It’s not clear if he hit a tree.

The boy was rushed to Children’s Hospital in Boston by a medical helicopter.

The extent of his injuries is not known.

His name has not been released.

WBZ-TV’s Paul Burton reports