What now

[btdt]

Watching a high school playoff game (NFHS rules)
Left field (300') has fence 20 feet high to keep balls out of neighbors yard
Ground rule is batted ball must go over fence for home run
Not just above the lower (8' high) wood fence the cyclone fence attach's to.
Sit
Don't remember # of outs
Runner R2 & R1
Batter hits ball 3/4 of the way up the fence down the left field line
PU has catch/no catch
As ball rebounds off of fence
R2 rounded 3rd
R1 just touching 2nd
A second ball now falls from the fence ten feet from the game ball
(must have gotten stuck at an earlier date)
There appeared to be no confusion of which was the game ball..................

As BU (in C position) or PU what do you do in this situation?
What rule do you use for your decision?

I will probably will never have this happen to me, but would like to have some type of answer in my knowledge base just in case