Looks like a loose ball play to me.
Enforce against A at spot of foul using all-but-one principal.
Enforce against B at previous spot.
It is a "loose ball", it is not a "loose ball play". Big difference.
A loose ball play is:
- A free kick or scrimmage kick other than post-scrimmage kick fouls.
- A legal forward pass.
- A backward pass (including the snap), an illegal kick or fumble made by A from in or behind the neutral zone prior to a change of team possession.
- The run or runs which precedes such legal or illegal kick, legal forward pass, backward pass or fumble.
Everything else is a running play, even if the ball is loose.