The AP report by Ibrahim Barzak buries that little tidbit three paragraphs in, after 95% of readers have stopped reading. The phrases "Israel's onslaught" and "tearing bodies apart and staining streets with blood" - that's in the first paragraph. The part where it happened because Palestinians were using human shields - paragraph 3:

Two residents of the area who spoke by telephone said they saw a small group of militants firing mortar rounds from a street near the school, where 350 people had gathered to get away from the shelling. They spoke on condition of anonymity for fear of reprisal.

Therein proceed 19 more paragraphs about the horrors of the Israeli attack - explosions, blood, literal gnashing of teeth and rending of garments - before we get more details about how "Cast Lead's Qana" was the result of Hamas's war crimes:

Two residents who spoke to an AP reporter by phone said the two brothers were known to be low-level Hamas militants. They said a group of militants -- one of them said four -- were firing mortar shells from near the school. An Israeli shell targeted the men, but missed and they fled, the witnesses said, refusing to allow their names to be published because they feared for their safety. Then another three shells landed nearby, exploding among civilians, they said.

Israel is considering complaining the the UN about how Hamas is using UN facilities for incitement and military operations. Upon hearing the news Hamas people were said to be confused because UNRWA has been facilitating their terrorism for years. Plus Hezbollah got to do the exact same thing during Lebanon II, using UN personnel as human shields and then having international media outlets blame the resulting deaths on Israel. So what's the big deal? (h/t: MR reader Matt)

References:
* Israel shells near UN school, killing at least 30 [AP]
* IDF shell kills 30 in Gaza UN school; Israel mulls appeal over Hamas fire from UN facilities [Ha'aretz]
* UNRWA Pours Millions Into Terrorism, Blames Israel (Plus: UNRWA Complains That Israel Is Blocking UNRWA Funding. Hmm) [MR]
* UN Peacekeepers Begged Hezbollah to Stop Using Them As Human Shields. UN, LA Times Blame Israel Anyway. [MR]

Previously:
* Hamas Bombs Another Israeli School (Plus: What's Their Next "Surprise"?)
* Hamas: We Will Murder Jewish Children All Over The World (Plus: Diplomats Trying To Stop The IDF From Winning)
* France 2 Indulges In Some Fauxtography, Says "Dozens Of Dead Bodies" From 2005 Hamas Explosion Are Cast Lead Victims