Carlos Hathcock was the most famous U.S. sniper during Vietnam. He shot at the reflection of the VC sniper's scope and his shot went through the scope's lens into the snipers eye.
I was going from memory...
I actually had his last name in my head. Just wasn't sure about his first name.
That was an amazing encounter that he had and the position of both and the change in the sun angle made the difference.