violation or not

[umpire29]

heres the senerio at the end of 2nd quarter a three point shooter team A get fouled no time left on clock. I have players go to there benches. they make the first free throw while attempting the 2nd one team A's players and coaches get up walk down the out of bounds side line the shooter is shooting at. is this a violation or not? and where might i find this in a rule book.