Huddled in the playground because the building was full, he struggled to separate rumor from reality. Phone lines were patchy, the power was out and air strikes were thundering all around. In any case, the 31-year-old had two adult brothers with cerebral palsy to consider. The family had left their home with a few bags after a previous evacuation call and didn’t know where else to go. He decided to stay put.

“It’s dangerous to move south. It’s too far,” he said by telephone, voice listless, before the connection dropped.

The United Nations said Friday the Israeli military had told its staff on the ground that all residents of northern Gaza — roughly half the territory’s population of over 2 million — had until midnight to relocate south. It called the task “impossible.”

Israel’s military spokesman Jonathan Conricus said early Saturday that it had observed a “significant movement of Palestinians toward the south” following the warning.

A 140-square-mile sliver of land on the Mediterranean, Gaza is ruled by the Palestinian militant group Hamas, but its borders are controlled by Egypt and Israel, which has declared a full siege, cutting off electricity and water. Crossings used to transport food are closed and discussions for a humanitarian corridor through Egypt have yet to bear fruit.

Read more: Protests Erupt Across Mideast as Israel Prepares Gaza Assault

Even before Israel called on civilians to leave Gaza City, the main population center, ahead of planned operations against Hamas, residents were running out of places to go.

Bombarded by thousands of Israeli aerial strikes since Hamas mounted its unprecedented attack on Israel nearly a week ago, more than 270,000 Palestinians had, like Dawoud, sought shelter in about 90 schools run by the United Nations Relief and Works Agency. With nearly a dozen mosques already destroyed, others had fled to hospitals and churches, or joined relatives living near the main UN compound in Gaza City, calculating it would be spared.

UNRWA, which serves Palestinian refugees, said 13 of its employees had been killed as of Friday. It’s moved its international staff and central operations from Gaza City further south and urged Israel not to strike its facilities.

Gaza health authorities said 1,900 people had been killed so far, including at least 40 Palestinians whose convoy was struck as they fled south. More than 423,000 people — almost 20% of Gaza’s population — were displaced before the evacuation order, according to the UN. It said tens of thousands had since moved further south and warned that “most people have no access to clean drinking water after supply.”

“Gaza is fast becoming a hell hole and is on the brink of collapse,” UNRWA Commissioner General Philippe Lazzarini said in a statement Friday. “The scale and speed of the unfolding humanitarian crisis is bone-chilling.”

‘Wipe Out’ Hamas

With Israel in shock after an assault that’s killed more than 1,200 people, Defense Minister Yoav Gallant has vowed to “wipe Hamas off the face of the Earth.” Saturday’s multi-pronged attack saw rockets rain down on Israel and gunmen maraud through Israeli villages killing and kidnapping civilians and soldiers, and ambush party-goers at a music festival.

As images emerged of children and elderly people being snatched from the streets, Israel formed a war cabinet to uproot the armed group altogether. It’s amassed 300,000 reservists, ready for a widely-expected ground offensive. More than 2,000 Palestinians were killed when Israel last invaded Gaza in 2014. This time, the fate of scores of hostages hangs in the balance and complicates Israel’s mission.

That’s raised the prospect that Israel’s vengeance for the Hamas attack will unleash a humanitarian catastrophe on the Palestinians.

Hamas, which is designated a terrorist organization by the US and European Union, rejected Israel’s calls for the people of Gaza to leave their homes. The group, which has governed the enclave for 16 years, often operates out of heavily-populated areas, making it virtually impossible to avoid civilian casualties, even with a 24-hour warning.

Reduced to Sand

Yousef Hammash, an advocacy officer at the Norwegian Refugee Council and a documentary-maker based in Gaza, said hundreds of families had rushed to the Latin Patriarchate of Jerusalem compound which includes a church, convent and school, as well as the Arab Orthodox Social and Cultural Center.

He fled himself to stay with relatives in the comparatively well-to-do Rimal neighborhood where the UN has its headquarters. But entire blocks of Rimal, Arabic for ‘sands’, have already been destroyed.

“Sections of Rimal have been reduced to sand,” said Hammash. “People are literally running for their lives.”

In the chaos, the Al-Shifa medical complex has emerged as a magnet for those who’ve found schools and churches too full to accommodate them.

Nowhere to Go

Ghassan Abu Habel said he initially fled from his home to his in-laws’ house in Al-Karama, north of Gaza City, thinking it would be safer.

“But a rocket fell just outside the house; it was a phosphorus bomb. We extinguished the flames with sand. Then another artillery shell. We rushed inside the house as F-16 air strikes rocked the area, shattering windows and causing shrapnel injuries to my face,” he said, adding that he had 20 stitches.

Huddled with his wife, children, and in-laws, about 20 people in total, in the pitch-black house, they finally resolved to flee. However, it was still dark outside, and rockets continued to rain down.

His wheelchair-bound father-in-law and elderly mother-in-law slowed their progress through a hellscape of rubble. They sought refuge in a neighbor’s house, resigned to perish together before ambulances arrived to rescue them from this “nightmare.”

The UN-run schools were already full, so the ambulances proceeded to a small pediatric hospital, only to find it already overflowing.

The Hospital

Finally, the ambulances deposited the family at Al-Shifa Hospital, where hundreds of displaced people had already filled the premises, camping in the carpark and staking out patches of hallways and wards.

Men loitered helplessly in the hospital’s grounds as incoming ambulances blared their sirens and the sound of explosions reverberated in the background.

Inside the hospital, women and children filled corridor floors as doctors rushed back and forth to tend to wounded or lifeless bodies carried on stretchers or by wailing relatives. With beds occupied, many casualties were receiving care on the bare floor.

But Al-Shifa Hospital is inside the area covered by Israel’s evacuation warning.

The director, Mohammed Abu Silmiya, who warned the hospital was running out of surgical and medical supplies and was down to two days worth of fuel to run its generators, said he could not abandon hundreds of patients dependent on ventilators, dialysis and intensive care.

“I have nowhere to take the wounded, the children, the women and the dead,” he said. “We can’t vacate the hospital. Let them invade wherever they may.”