According to the New York Times, a 16-year-old boy was critically injured while riding on a school bus, which was hit by laser-guided missile launched by Hamas. The Times reports that in addition to claiming responsibility for the attack, Hamas said it intentionally chose the its target in revenge for an Israeli attack that left three “holy fighters” dead.
By calling its dead “holy fighters,” Hamas obliquely acknowledges that the Israeli attack was on a legitimate military target. And by stating that that it intentionally attacked a school bus, which is clearly a civilian target, Hamas has admitted to committing a war crime.
It doesn’t get any clearer than this.