President Joe Biden said on Thursday that he believes negotiations for a possible truce between Israel and Hamas will be complicated by an incident where Gaza officials say Israeli troops killed more than 100 starving Palestinians trying to access aid.

Earlier that day, Israeli forces in Gaza City fired at a crowd of Palestinians after the enclave’s northern region received its first major aid delivery in a month. Hundreds of Palestinian civilians, who are being starved by the lack of aid, began pulling flour and canned goods off the trucks when witnesses said troops began shooting at them.

Medics found “dozens or hundreds” lying on the ground at the scene, Kamal Adwan Hospital official Fares Afana told The Associated Press. Because there were so many bodies, Afana said some of the victims had to be wheeled to the hospital in carts pulled by horses and donkeys instead of ambulances. Video taken by a Gaza journalist shows medics assisting a single donkey carrying a cart that has a pile of bodies stacked on top of each other.

The Gaza Health Ministry, which described the shooting as a “massacre,” said more than 100 Palestinians were killed and 760 were wounded. The casualties resulted in the Palestinian death toll surpassing 30,000, with another almost 70,500 wounded, according to health officials.

On Thursday morning, Biden told reporters before traveling to Texas that he had not yet learned what specifically happened in north Gaza, saying there are “two competing versions of what happened.” Israel confirmed that their troops fired at the crowd, but claimed they did so because the Palestinians — who are experiencing a breakdown of public order due to not having basic necessities — approached the trucks in a threatening manner.

When asked whether he’s worried the shooting will complicate negotiations for a temporary cease-fire deal, the president said, “I know it will.”

Israel launched its ongoing military offensive in Gaza immediately after Hamas militants attacked the country on Oct. 7, killing about 1,200 people and seizing about 250 hostages. Around 130 hostages remain — including roughly 30 believed to be dead — after the militant group released the remaining captives during a temporary cease-fire in November.

In addition to the massive death toll, Israeli forces have destroyed homes and important institutions like schools, hospitals, mosques and shelters. The offensive has also disproportionately targeted women, children, aid workers, doctors and journalists. Israel is facing accusations in international courts of committing genocide and apartheid against the Palestinians, which it fervently denies.

More than half of Gaza’s population of 2.3 million has been pushed to the southernmost city of Rafah, where Israel has threatened a ground invasion if a deal to return the hostages is not reached by the time the Muslim holy month of Ramadan begins around March 10.

The U.S. has vetoed three times a U.N. Security Council resolution that calls for a cease-fire in Gaza, causing massive backlash due to growing international calls for an end to the violence. The U.S. is separately working with Egypt and Qatar to secure a temporary cease-fire and the release of some of the hostages, though both Israel and Hamas have not signaled any progress on such a deal.

Biden previously said that he expected a deal as early as next Monday. But on Thursday, the president retracted his estimated timeline.

“Hope springs eternal,” he said. “I was on the telephone with people in the region. … Probably not by Monday, but I’m hopeful.”

The Security Council is expected to meet on Thursday at the request of Algeria to discuss the shooting in north Gaza, according to Al Jazeera.

The White House said that Biden spoke with leaders in Egypt and Qatar on Thursday to discuss the status of negotiations and the “tragic and alarming” shooting in Gaza City.

State Department spokesperson Matthew Miller told reporters that “too many Palestinians died today” in the shooting and that the U.S. is “pressing for answers.”

“Two things are clear: just from the aerial footage, you can look at that and right away conclude that the situation is incredibly desperate,” he said. “People are swarming these trucks because they’re hungry, because they need food, because they need medicine and other assistance. And that tells you that we need to do more to get humanitarian assistance in.”

Some pro-Palestinian groups who have been critical of the U.S. government’s role in Israel’s offensive demanded that Biden condemn the country for attacking the starving Palestinians.

“It is unconscionable that the Biden administration has not condemned the Israeli government for any of the war crimes it has committed over the past four months. Only political leaders who do not believe all lives are equally valuable could ignore today’s massacre and continue to enable this open genocide of Palestinian men, women and children,” Nihad Awad, national executive director of Muslim civil rights group CAIR, said in a statement on Thursday.

“The Biden administration must stop doubling down on its complicity in the Gaza genocide and offering vague words of mild criticism — that mean nothing to [Israeli Prime Minister] Benjamin Netanyahu — while it speeds more bombs that he will use to massacre more Palestinians.”

Israel has blocked food, water, medicine and other aid from coming in, except for a small number of supply trucks arriving from the south. According to U.N. humanitarian agency OCHA, aid organizations have been unable to reach north Gaza and “increasingly parts of southern Gaza safely” due to convoys coming under Israeli fire and because they have been “systematically denied access to people in need.”

The U.S. also cut funding this month for UNRWA — the only U.N. refugee agency operating in Gaza — including $300,000 of frozen funds that the government annually provides in humanitarian aid. The lack of funding, triggered by Israel’s allegations that a few UNRWA workers participated in the Oct. 7 attack, could lead to the agency shutting down and worsening the already catastrophic humanitarian conditions in Gaza.

Many of the more than 750,000 Palestinians remaining in north Gaza say they have resorted to desperate measures so they don’t die of starvation, including eating horses, animal feed and leaves. Still, the U.N. says that Palestinians in north Gaza are “one step away from famine,” and that 1 in 6 children in the north who are under the age of 2 suffer from acute malnutrition and muscle wasting.

“Intentionally depriving people of food is clearly a war crime. Israel has announced its intention to destroy the Palestinian people, in whole or in part, simply for being Palestinian,” Michael Fakhri, the U.N. special rapporteur on the right to food, told The Guardian.

“In my view as a U.N. human rights expert, this is now a situation of genocide,” he continued. “This means the state of Israel in its entirety is culpable and should be held accountable — not just individuals or this government or that person.”