Since the firemen left someone covering the front entrance, it was highly likely they were still on the first floor. Their team was small. If their goal was on a different floor, they wouldn’t have left anyone covering the front entrance; they would’ve all gone to that floor instead. But they left a guard, so all of them were probably on the first floor,
Objection, your honor, highly speculative... If she's right, fine, but then tell me afterwards. there's smart and then there's clairvoyant.

