AMNA NAWAZ: Today, Israeli missiles struck a U.N. school building where displaced Palestinians have been sheltering since the October 7 attack.

Israel says it killed Hamas militants there.

But Palestinians in the building say the victims were mostly women and children.

Nick Schifrin has our story.

And a warning: Some of the images in this piece are disturbing.

NICK SCHIFRIN: The classroom, that became a shelter is now shattered.

Two Israeli munitions hit their target, a room designed for the displaced, where they slept and where many have lived for months.

Outside the local hospital, a mother's grief.

Frial Zedan lost her 17-year-old son, Mahmoud.

FRIAL ZEDAN, Mother (through translator): There's nothing here but people, just people trying to live.

Why are you doing this to us?

NICK SCHIFRIN: Mahmoud's sister, Seham, is inconsolable.

SEHAM ZEDAN, Sister (through translator): Why would they bomb the school?

Why would they bomb any school?

Where do we go?

There's no place to go to where they don't drop missiles down on us.

Where do we go?

NICK SCHIFRIN: In another family, too young to understand why, old enough to mourn.

Palestinian health officials affiliated with Hamas say a dozen victims were women and children.

But the Israeli military said, and informed the U.S. in a private briefing, that the classroom had been taken over by 20 to 30 Hamas and Palestinian Islamic Jihad militants who had participated in the October 7 terrorist attacks, planned -- quote -- "imminent attacks," and turned the three classrooms in the U.N. school into their command-and-control.

Israel said it dropped small bombs that did not damage nearby rooms, or kill civilians.

And, in a briefing, Rear Admiral Daniel Hagari displayed the names of Hamas members who'd been killed.

REAR ADM. DANIEL HAGARI, Spokesperson, Israeli Defense Forces: Hamas hopes the international law and public sympathy will provide a shield for their military activities, which is why they systematically operate from schools, U.N. facilities, hospitals, and mosques.

NICK SCHIFRIN: Today, State Department spokesman Matt Miller called on Israel to be transparent.

MATTHEW MILLER, State Department Spokesman: Even if the intent is what the IDF has said publicly, that they were trying to use a precision strike just to target 20 to 30 militants, if you have seen 14 children die in that strike, that shows that something went wrong.

That said, these are all facts that need to be verified.

And that's what we want to see happen.

NICK SCHIFRIN: Back in the hospital, Samia Al-Maqadmeh cradles her son Imad, who was rescued from the rubble.

IMAD AL-MAQADMEH, Wounded in Airstrike (through translator): What did we do?

There are no armed people in the school.

There are children who play, like us, children.

Why did they bomb us?

I want to know why.

Where should we go?

NICK SCHIFRIN: Israel said it has struck five U.N. facilities being used by Hamas as shields in the last month alone.

The U.N. said today that, since the war began, 180 of its buildings have been struck, killing, Amna, more than 450 of the displaced.

AMNA NAWAZ: Nick, this leads us all to wonder, what is the status of those cease-fire talks?

I know you have been reporting on those previously that, in the first phase, it would halt the war for six weeks, release 30 or so hostages.

Where are those talks?

NICK SCHIFRIN: A senior administration official and regional officials tell me that Qatari and Egyptian mediators have met with Hamas in the last 24 hours.

The administration official I spoke to called the talks -- quote -- "constructive" and say a formal response to that Israel-backed President Biden-announced plan could come in the next few days.

But behind the scenes, diplomats from the region and analysts are very pessimistic, in part because of the public statements that both sides are making.

Hamas continues to demand the transition in that three-phase plan from phase one to phase two include a permanent guaranteed cease-fire, something that, of course, that we have been talking about Hamas has been demanding for a long time.

And the deal only has an Israeli commitment to maintain a temporary cease-fire so long as talks continue.

And, on the other side, Israeli Prime Minister Benjamin Netanyahu continues to say that his demand is the -- quote -- "elimination of Hamas."

So, the public divide continues.

But a U.N. diplomat tells -- goes further, telling me that both sides appear to be more interested in blaming the other side for a failure in the talks than actually making any progress.

And some U.S. officials are increasingly worried that Netanyahu wants to wait or wants the war to continue until the U.S. elections, because he believes that he can get a better deal under President Trump.

And these officials are worried that Hamas thinks it's winning and see no interest or reason to make a deal.

But the U.S. is continuing to try and keep diplomatic pressure.

Today, the White House released a statement from 16 countries, many of whom -- many of whose citizens are hostages still -- quote -- "There is no time to lose.

We call on Hamas to close this agreement that Israel is ready to move forward with and begin the process of releasing our citizens."

And the U.S. is also trying to get through a U.N. Security Council resolution that would back these principles in the hostage deal.

But it's not clear Israel is behind that either.

AMNA NAWAZ: Sobering update.

Nick Schifrin, thank you, as always, for your reporting.

NICK SCHIFRIN: Thank you.