What we know about the 22 Americans killed in the Israel-Hamas war

At least 22 Americans have been killed in Israel as the Israel-Hamas conflict continues, according to the U.S. State Department.

"As we continue to account for the horrors of the appalling terrorist assault against Israel this weekend and the hundreds of innocent civilians who were murdered, we are seeing the immense scale and reach of this tragedy," President Joe Biden said in a statement on Monday.

The statement continued, "It's heart-wrenching. These families have been torn apart by inexcusable hatred and violence...My heart goes out to every family impacted by the horrible events of the past few days."

It's currently unclear how many Americans are among those missing or might have been taken hostage, but Biden said in a statement on Monday that it's "likely" American citizens are being held hostage by Hamas.

Here's what we know about the U.S. victims so far:

Hayim Katsman, 32

The first American citizen identified is 32-year-old Hayim Katsman, who had been living in Israel, his mother told ABC News.

Hannah Katsman said she initially thought her son had been taken hostage, but later learned he had been killed when Hamas militants burst into his apartment.

She said he and a female neighbor were hiding in a closet when they were found. The neighbor was released but her son was shot dead and his body was found in his apartment, she said.

"[I've] been getting so many messages from people who worked with Hayim or who knew him, or who met him during their travels and how warm he was, how open," Hannah Katsman told ABC News. "He was a very accepting person and [a] very loyal friend, good sense of humor. He took things in stride."

According to the University of Washington's Henry M. Jackson School of International Studies, Hayim Katsman received his Ph.D. in 2021 with his research focusing on "the interrelations of religion and politics in the Middle-East, focusing on Israel/Palestine."

Lotan Abir, 24

Lotan Abir, 24, from Utah was confirmed as one of the Americans killed in Israel by Rabbi Avremi Zippel to ABC4 and the social media platform, X (formerly known as Twitter).

Zippel said that Abir, who had been living in Israel for the past nine months, was attending a rave with a group of friends on Oct. 7 near the border with Gaza when Hamas attacked. Abir was killed, but his friends are said to have survived.

U.S. Sen. Mitt Romney released a statement offering his condolences to the family.

"The horrific, inhumane, and depraved terrorist acts perpetrated by Hamas against Israelis have touched everyone around the world," he wrote. "Today, news of the loss of one of our own from Utah further tears at our collective heart. I offer my deepest condolences to the family and friends of Lotan Abir -- may he rest in peace.

Deborah Mathias

Deborah Mathias, an American who lived in Israel, was confirmed killed along with her husband, Shlomi Mathias, their teenage son confirmed to ABC News.

Rotem Mathias, 16, said that when Hamas militants stormed into their kibbutz in southern Israel last Saturday, he helped his parents barricade the doors of their home with anything they could find -- mattresses and tables, but it wasn't enough.

The militants opened fire on their house, spraying bullets through the window. Rotem Mathias' parents jumped on top of him to protect him from the gunfire.

"The terrorists shot open the door," Rotem Mathias, a dual Israeli-American citizen, told ABC News in an interview that aired Wednesday on "Good Morning America."

"They throw a grenade or something that exploded," he continued. "The last thing my dad said is he lost his arm and then my mom died on top of me."

ABC News' James Longman contributed to this report.