opponents go to locker room before FT's are shot

[MJT]

Here is the situation told to me by a friend of mine. With time running out in the first half player A1 heaves a ¾ court shot. Player B1 whacks A1 in the arm as he is launching his 2 handed heave. Time expires before the clock is stopped. Coach of B takes all his players to the locker room.

Is it fine for B to leave the court and go to the LR before the FT's are shot or do they need to stay on the floor until the FT's have been shot? There is no time left, so nothing will occur after the FT's but the half time will begin. If we have a T, do we have one, or one for each of the 5 players who left the floor?