Martin Flagg answered every question the FBI agents had. Yes, he omitted the part about Walter summoning ghosts and the guys saving him but they didn't really seem interested in that. They were more interested in the deaths during filming and would investigate them, not that anybody had really missed Ray or Brad. And the series of deaths had been exactly what the movie needed to get a bigger following.
Before the agents had the opportunity to go away he asked the part he was interested in. "Gentlemen, do you know if anybody has the movie option for their case..?"