Forces of Kick

[BigGref]

I got a situation from last year that I would like to bring up again.

4th and 7 from A's own 15. A1 lines up to kick, recieves ball, kicks and is blocked by B1. Ball rebounds and comes to rest at A's 5 yd line.

Here comes a member of each team running toward the ball, Member of B gets there first and jumps on the ball causing it to go into the endzone, where A jumps on it and causes it to go out of the back of the endzone.

Who's ball, where, why? (with refererences if possible, thanks)