The questioner tried to "set a trap", so that if RJ wouldn't be careful and just answer e.g. with "before", the questioner could directly deduce that this must mean that Slayer is the killer.

Of course, RJ and the audience immediately saw through this attempt and therefore laughed. However, "challenged" like this, RJ decided to counter with a witty and clever question himself. Of course, the result is the same, as if RJ had simply answered with a dry RAFO; we don't know the answer yet. RJ basically acknowledged, though, that it was a nice try by the questioner through his screwing with his head-comment.

It also seems very far-fetched to me that RJ never considered if Slayer can take things with him to TAR.