Thanks guys.
My son was very happy. I asked him if he realized what he had accomplished and I believe he understands. He said when he drew she threw her head up and he thought he was busted. About that time a cow walked through and drew her attention. He exclaimed he knew he was busted and it was the longest 10 seconds of his life holding full draw till she settled back down..
He has been bow hunting for three years so he has had plenty of lessons in what can go wrong.