UN School explosion - legal attack on military objective or illegal attack on civilians?

The Jerusalem Post reports:

At least 30 people were reportedly killed and 53 wounded in an
explosion in a UN-run school in the town of Jabalya in the northern Gaza Strip,
according to Palestinians. The IDF issued a statement saying the school grounds
were used by terrorists to fire mortar shells at the troops. According to the
IDF, among the dead were members of a Hamas launching cell, including operatives
Immad Abu Askar and Hassan Abu Askar.

The infantrymen returned mortar shell fire into the school grounds, the
army said. Defense officials told The Associated Press that booby-trapped bombs
in the school triggered the secondary explosions which killed scores of
Palestinians on the site.

No doubt many will attack Israel for killing civilians in a UN-run school. Probably, most of the dead are civilians, many undoubtedly are children. Once again the Hamas terrorists used a school as shelter for mortar operations against Israel. It appears that the terrorists planted booby-trapped bombs in the school with the expectation that IDF soldiers would be killed by them when the Hamas fighters withdrew.

Instead, fire from the IDF exploded the booby-trap bombs that killed the Palestinians. Hamas bombs intended for Israelis killed Palestinian civilians rather than IDF weapons fire.

Responsibility for all of the civilian deaths lies with Hamas. Hamas intentionally used civilians as shields to attempt to deter Israeli military response to the mortar attacks. What alternative did the IDF have? They could not allow the Hamas mortar crew to continue to fire at will on Israel and IDF troops.

Furthermore, it was not indiscriminate Israeli fire that killed the Palestinian civilians, but Hamas bombs. Undoubtedly, Hamas enablers will carefully avert their eyes from the facts and attack Israel for killing civilians.