Yep. Most likely a Hamas oopsie, followed closely by Hamas doing it on purpose. Israel doing it is a distant third, but frankly I wouldn't care if they did it. Hamas has no soul; they put their military structures in hospitals and other civilian areas in direct contradiction of the rules of war, because they rely on our reacting with western values. They are not human, as we define human. They take pipes we send to improve the water supply, the supply they soiled with their tunnels, and they turn them into fusilages for rockets. They take concrete for infrastructure and turn it into more tunnels. They use their people as human shields, and they prevent them from leaving, because they need the shields.
Give people as much time as practical to leave, into Egypt or one of their many Arab brethren countries (but shockingly, they won't let them in, because they don't want the Hamas cancer spreading into their countries. This also is Israel's fault I presume). Anyway, let people get out who can, then turn Gaza into a sheet of glass.
There is no "oh noes, the reciprocation!" One side seeks out and burns and tortures babies, rapes and kills women, and uses their people as shields. The other attacks the military, which is placed in civilian areas, and in doing so kills some civilians. You are on one side or the other; "can't they all just get along" is childish and impossible.
If Hamas dropped their weapons today, there would be peace tomorrow. If Israel dropped their weapons today, they would all be dead tomorrow.
There is no moral relativism with evil, and there is no negotiating with Hamas. They do not want land, they want to kill all the Jews. They proudly say "you celebrate life, we celebrate death." Just end them already and give them what they want.