Here's M.D. Jennings of the Packers going up and getting the football, and appearing to come down to the ground with the football.
Then there's the view from behind, which again makes it look like Williams never loses control of that football when he's on his way down to the ground.
Then you have this view, which shows Golden Tate fighting for the football in a desperate attempt to gain simultaneous possession of the football. Technically, simultaneous possession is not applicable in cases where one player takes control of the football and the second player then wrests control away afterwards.
However, the NFL officials on the scene ruled otherwise. At least one of them signaled touchdown, and that was the call on the field. Since it was ruled simultaneous possession, the touchdown was preserved because simultaneous possession is an unreviewable act.
Regardless, Seahawks quarterback Russell Wilson is impressed with himself, and he should be. He might have just thrown the first ever game-winning touchception in NFL history.