The investigation is over. Everything is known.
Dr. Gage has wisely restricted his own investigation into the physical collapse of the buildings, and he has not addressed the question of who did it.
He advocates an investigation to "find out" who did it.
Not everybody has avoided investigation of the perpetrators. The events currently unfolding are removing them from power.
A show trial, as Dr. Gage requests, may or may not take place, but nothing can stop what is coming.