mold on sheetrock
You've got two problems. First, the drywall got wet enough to grow mold, meaning that the moisture level remained above 60% or .6 water content for greater than 72 hours. That means that it was wet long enough to compromise the strength of the drywall. Second, drywall is very porous and contains enough organic material that the mold has worked it's way well into the sheets. You will never kill what is already embedded. If you use this, and it gets rewetted, the dormant mold will reappear very quickly. The 72 hour window won't apply. If you try to salvage any of it, go 12" past the last sign of mold. I would not plan on using it as is. No matter what you spray on it to kill the mold, it will not penetrate deep enough to eradicate all of the mold components.