1st and 10 at the 50 yard line. A-12 takes the shotgun snap and drops back to pass. Blitzing LB B-55 as he's being blocked reaches over the blocker and grabs A-12 by the facemask taking him to the ground at the A-40 yard line. We've got an immediate flag for PF-Facemask.
What is the penalty enforcement? Down, distance, and rule(s) reference please.