It is WRONG for any group (and this Salafist group in Gaza claimed responsibility for the rockets during Obama's visit, most likely the same this time) to aggress, especially towards civilians (war crime), period. As Hamas is the governing party in Gaza, it is their responsibility to catch, charge & prosecute those individuals in that group. Before Israel starts bombing, it should give Hamas time to do that, and communicate with Hamas through Egypt. This was the way the cease-fire was made, this is the method prescribed within it to mediate disputes or events such as this. Take advantage of that instead of initiating and prosecuting another bloody, ugly, costly conflict.
UN warns Turkey against calling buffer a 'safe zone' unless guarantees civilians' safety (Reuters)