Deadly attacks committed by either Palestinian or Israeli civilians against the civilians on the other side are murder. There is no justification for such attacks under any law. It's likewise murder when a combatant on either side targets civilians. 

To be sure, there have been examples of that over the six-decade course of this conflict, but relatively-speaking the numbers are low. This is true even during the worst periods of civilian-on-civilian violence. (That's not said to excuse it in any way.)

The only time that large numbers of civilians die- and they're always Palestinians- is when Israel mounts its "grass-cutting" attacks. These are the full-scale military assaults that Israel commits, using heavy weapons, naval vessels and aircraft, against Palestinians in urban areas.