From Israel's POV they warned civilians to get out, the part of the camp they hit was being used as a military base. Hamas attack Israel, Israel go to war to eliminate hamas so they don't attack again. They hit targets. Hamas cover them with civilians. Hamas refuse to surrender and wont give back hostages.
It is so sad and awful but Israel is not breaking any laws here. You may not like or agree with the laws but Israel is not breaking any.
I actually really do blame Hamas for all of this. The rest of the blame lies in any policies that allowed hamas to become so embedded in Gaza that to root them out now means killing thousands of civilians.