The elementary school called with an urgent message about her son. “The war has started,” she was told. Come pick him up.

The mother, who asked not to be identified, said she had only just dropped the boy off and couldn’t leave immediately since she had patients to see in her job as a midwife. Then the earth shook. And she ran.

It was too late. Three airstrikes had hit Shajareh Tayyebeh elementary school in Minab, killing 168 people, according to the town’s mayor. Many of them were children. One of them was her son.

“By the time we arrived, the entire school had collapsed on top of the children,” the mother told NBC News. “People were pulling out children’s arms and legs. People were pulling out severed heads.”

Four days later, grief and outrage grew over the school deaths, which has become a flashpoint for opposition to the U.S. and Israeli strikes. There is also anger and uncertainty over the fact that no one has admitted responsibility for the most-publicized civilian casualties since the start of the war.

A large crowd gathered to bury the children Tuesday, video and images published by state media show. There is a mass burial with rows and rows of what appeared to be individual graves dug side by side.

The U.S. and Israel have since hit thousands of targets inside the country, killing Supreme Leader Ayatollah Ali Khamenei among nearly 800 others, according to the Iranian Red Crescent Society.

Tehran is striking back, hitting Israel and several other countries in the region allied with the U.S., including the United Arab Emirates, Saudi Arabia, Qatar, Oman and Bahrain. Six U.S. service members were among those killed in its counterassault, as well as 11 people in Israel, while dozens have been killed in Israeli strikes against Hezbollah in Lebanon.

When asked about the deaths on Monday, Secretary of State Marco Rubio told reporters that U.S. forces “would not deliberately target a school,” adding that the Defense Department “would be investigating ​that if that was our strike.”

Over the weekend, U.S. Central Command, or CENTCOM, said it was looking into reports of civilian deaths. The Israeli military has so far declined to comment.

The school appeared to have been located near an Islamic Revolutionary Guard Corps (IRGC) site, according to satellite footage, which British broadcaster BBC News reported has previously been targeted.

Both the Minab official and the mother who spoke to NBC News said the school facility was built on an IRGC base. The base closed around 15 years ago and all military personnel were moved, although the school stayed open, they said.

Satellite imagery from 2011 appears to show the building as part of the same compound, before being fenced off later.

Ali Farhadi, spokesperson for Iran’s education ministry, said on Sunday that three attacks had struck the school, which he said had 264 students.

Iranian Foreign Minister Abbas Araghchi said Saturday on X that the school had been “bombed in broad daylight, when packed with young pupils.”

“These crimes against the Iranian People will not go unanswered,” he warned.