Double foul after interception

[jTheUmp]

This is a bit of a trick question... it took me 30 minutes of rulebook reading, 7 times of reading one rule word-by-word like a 2nd grader, and an email to my association's clinician before I figured out what the rule says should be done.

Using Fed rules, 9th grade game:

3rd and 8 at midfield.
Pass is intercepted by B1 on B's 40-yard line.
During the return, B2 holds A3 at B's 45 yard line.
A4 commits a 15-yard facemask foul on the runner (B1) at A's 30 yard line.

How do you enforce the penalties?

For bonus points, how is this enforced in NCAA?