A Palestinian girl walks past an UNRWA vehicle close to a mosque partially destroyed during an overnight Israeli military strike, on July 22, 2014, in Rafah, the southern Gaza Strip. U.N. Chief Ban Ki-moon and U.S. Secretary of State John Kerry are in Cairo in a bid to broker a truce between Israel and Hamas after two weeks of fighting that has left over more than 1,000 Palestinians dead. SAID KHATIB/AFP/Getty Images

GAZA CITY, Gaza Strip -- On Wednesday morning, Ala Bes sat with his three children on mats outside the UNRWA school in Jabaliya, where they had been living as refugees. The school, used as a shelter by the United Nations agency, had been hit the previous night by what it said was Israeli artillery fire, killing 15 people, including children. Bes and his family had spent the previous night awake. For a while, he said, there was no one there to help -- the school was pitch black, its electricity cut and wails from inside the collapsed classrooms shuddered throughout the complex.

“If we thought this place, an UNRWA school, would be bombed, we never would have come here,” Bes said.

The United Nations Relief and Works Agency, which people here simply call “the agency,” is Gaza’s second-largest employer, with 30,000 people working for it throughout the Strip. For years, Palestinians in Gaza have relied on the organization to watch over them, to provide anything from education to health care to social services, to help with things from funds to emergency shelters. In past conflicts, UNRWA has been able to provide. But this time, in this war, it is unable to handle the massive number of displaced people. It says it can no longer meet its mission without significant financial support.

Palestinians living at the school shelter in Jabaliya said Wednesday it took more than an hour for the ambulances, escorted by International Committee for the Red Cross and UNRWA staff, to show up, though several UNRWA security guards were on the scene at the time of the strike. One of them was killed. For an hour, those living at the school waited to see who had survived and who had died. When the ambulances finally arrived, there was no telling who could have been saved if they had come earlier.

The school in Jabaliya, one of 85 UNRWA shelters in Gaza, was the sixth to be targeted since the Israeli military operation against Hamas in Gaza began July 13, and the second school to be hit in one week. The attack is an example of the increasingly desperate humanitarian situation here, and a testament to UNRWA’s dwindling ability to shelter and provide security for the internally displaced.

At the beginning of the military operation, UNRWA issued a statement warning that it had the capacity to host only 50,000 people in shelters in the Strip. It is now sheltering more than 200,000, and according to employees, is having a difficult time handling that number. It has no space left.

On Thursday Valerie Amos, the top U.N. humanitarian official, said that the situation in Gaza was “dire.”

“We have not been able to get in front of the curve to provide assistance,” Robert Turner, director of the UNRWA Gaza office, said in an interview.

After the attack on the UNRWA school in Jabaliya, Christopher Gunness, the agency’s spokesman, said that it had “reached its limit.” “Soon there will be hundreds of thousands living in the streets,” he said. Gunness appeared on an Al-Jazeera segment shortly after the attack and broke down in tears when trying to describe the human impact of the conflict.

As the conflict rages on, the organization fears what could happen with another massive displacement from somewhere like Jabaliya.

“We are going to do everything we can to the best of our ability, but we don’t have infinite capacity,” Turner said. “We surprised even ourselves. No one thought that we would be able to handle even this many people.” If another massive displacement occurs, Turner said that Israel would be legally responsible for managing it.

For now, UNRWA is still trying to squeeze some more people into its shelters, but there are already almost 30 people to each classroom in school shelters. UNRWA is so overwhelmed with people that it is beginning to send the displaced to shelters run by the Palestinian Authority.

“These schools are not designed to be shelters,” he said. “There is no running water, no electricity. They are not equipped.”

The UNRWA school in central Gaza City shelters about 1,500 people, according to an UNRWA education liaison there. There are 10 staff members at the school.

One man, a security guard wearing an UNRWA vest, sat outside of the school’s front gate.

“I have been here for about 20 days,” he said. “When I came here, they asked me if anyone would volunteer to man the gate. They haven’t paid me yet, but maybe they will soon.”

But UNRWA is low on funds. The Agency said it had begun the year with a $65 million cash deficit.

The organization is not funded like other UN organizations. Almost all of its funding comes from voluntary contributions, mostly from donor states. When UNRWA was formed in 1949, it was established as a temporary agency that would collect voluntary contributions of any amount from member states. Therefore, there is no set amount of money that the organization receives from the United Nations each year, though the U.N. does cover senior international staff salaries.

The current conflict increased that deficit significantly. Turner said the agency is now asking for $187 million to cover the costs of two months of conflict and six months of reconstruction.

For weeks, the organization has warned that the humanitarian situation was growing dire. Almost every day UNRWA publishes a situation report, which indicates how many people it is sheltering and how many shelters it is operating, as well as its main concerns for the displaced population. In almost every report since the beginning of the conflict, UNRWA has said that it was growing increasingly weary that it would not be able to host the massive amounts of displaced people.

Several other humanitarian organizations besides UNRWA are operating in Gaza, including the World Health Organization and ICRC. Maria Cecilia Goin, a spokesman for ICRC, said the organization, like UNRWA, was facing massive setbacks, one of them being that it cannot easily reach the wounded. Palestinians at the UNRWA school in Jabaliya said ICRC, like UNRWA and the Red Crescent, also did not come to the scene of the attack for more than an hour.

Goin said that her organization needs to first alert officials with the Israel Defense Forces and Hamas, the Islamist radical group in power in Gaza, to coordinate entrance into the zone of the fighting.

“They need to give us the OK on both sides,” she said. “We need to wait a long time because the fighting is going on. In some cases, it's impossible to do our humanitarian work because we cannot go until both sides agree.” Goin said ICRC has about 40 ambulances, but almost half have been disabled by the fighting.

International leaders have called for an immediate cease-fire in Gaza, but Palestinians here are not hopeful. Even if there were a cease-fire, Turner said, there would still be massive displacement in Gaza. Unlike past wars, he said, there is no formal government structure to help rebuild.

“This time, no one is in charge here. In the last war, we could see the end," Turner said. "This time, we can’t end the conflict and expect things to go back to normal. It is inconceivable for us to go back to the way things were.”