You do know the answer and you have come here for "confessional".
The integrity of the game (And safety of the players) is in jeopardy if you do not step up on this situation. I had a similar play last monday.
I am "new" Trail on the non-bench side, fast break on tableside. My partner is a little late on the break and is straightlined. A1 drives to the hoop (on Team B's end) as B1 attempts to take the charge, but arrives late. I hesitated long enough for my partner to take the play with a late whistle and it did not come so I called it.
As I reported the foul, I heard B's assistant coach (JV Coach, and a state-certified offical) asking "Who is watching the other players?"
I then stepped closer to the head coach and discreetly told him, he needed to have better control of his bench personnel. Not a peep from the bench the rest of the way.