A Loose Ball is a live ball that is not in player possession, i.e., any ball that has been kicked, passed, or fumbled. A Loose Ball is considered to be in possession of the team (offense) whose player kicked, passed, or fumbled it. It is a Loose Ball until a player secures possession or until the ball becomes dead. If it has not yet struck the ground, a Loose Ball is In Flight.
The ruling on the field is complete.
A player who makes a catch may advance the ball. A forward pass is complete (by the offense) or intercepted (by the defense) if a player, who is inbounds:
An official shall declare the ball dead and the down ended when a runner is contacted by an opponent and touches the ground with any part of his body other than his hands or feet. The ball is dead the instant the runner touches the ground. A runner touching the ground with his hands or feet while in the grasp of an opponent may continue to advance; or if, after contact by an opponent, any part of a runner’s leg above the ankle or any part of his arm above the wrist touches the ground, the runner is down.