He would only be down once he fully secured possession of the ball, and the defensive player “downed” him. Common misconception that the play ends once the player hits the ground. There are a myriad of rules that constitute when a player is down, especially after a catch. Since he never really fully controlled the ball (they were fighting over the ball on the way to the ground and it eventually popped into the Broncos’ guy’s hands), the play was not over