Warning: the following contains graphic descriptions of violence.

(NewsNation) — For seven hours, Lee Sasi hid in a bomb shelter and under dead bodies following an attack on an Israeli music festival Saturday when Hamas militants tore through the crowd, killing at least 260 people.

Sasi described it as a “nightmare.”

“Everybody was dying in front of me,” Sasi, an American woman from California, told NewsNation’s Chris Cuomo, who was reporting live from Israel on Tuesday.

She was among the survivors who were attending the Supernova music festival, where some 3,500 people gathered in the Re’im kibbutz in southern Israel, only a few miles from the border with Gaza. Many are still missing, possibly captured and taken to Gaza.

When the attack first began Saturday morning with a barrage of rockets flying overhead, Sasi says she didn’t know what was happening.

“We arrived to the party and we were dancing and we were taking pictures and then we just saw, up in the sky, it looked like fireworks,” Sasi said.

When they realized it wasn’t, they fled the party to go to a nearby bomb shelter.

Then, she says, gunmen showed up.

“Our friend Alex who came with us, he stood up front, he guarded the entryway of the bomb shelter, and they immediately just started shooting at everyone who was in front; maybe 10 people fell down instantly in front of my eyes,” Sasi said. “After that, they were throwing grenades, and when the grenade fell, it blew up my uncle right in front of my face while he was protecting me.”

Sasi is one of the many Israelis who have described the atrocities that occurred Saturday when Hamas launched the largest-scale attack on Israel the country has seen in decades. More than 1,000 Israelis have died in the attacks, and some 150 are believed to be held hostage in Gaza.

At the festival grounds, Sasi spent upwards of seven hours hiding under dead bodies as the sounds of explosions and gunfire rang out around her.

“It felt like an eternity,” she said. “I feel deaf in my left ear, but I’m so grateful to be alive.”

President Joe Biden confirmed Tuesday that Americans are among the hostages. He vowed to provide Israel with whatever support it needs and condemned the attack, saying “there is no justification for terrorism.”

Hamas responded to Biden, saying his administration should “review its biased position” and “move away from the policy of double standards” over Palestinian rights to defend themselves against Israeli occupation.

A spokesman for Hamas characterized the incursion as a “legitimate resistance” in an interview Monday with NewsNation.

Israeli rescue services say at least 260 bodies have been recovered from the site of the festival, but the death toll may rise as searches for the missing continue, Al Jazeera reported.

The attack is believed to be the worst civilian massacre in Israeli history.

“I hope the world can see this, and I hope this will make a difference,” Sasi said of sharing her story of survival. “It was a walking miracle.”

The Associated Press contributed to this report.