Sgt. Benjamin N. Pennington, 26, was killed in Saudi Arabia.
President Donald Trump announced "major combat operations" against Iran on Feb. 28, with massive joint U.S.-Israel strikes attack targeting military and government sites, officials said.
Iranian state television confirmed that Ayatollah Ali Khamenei was among those killed in Tehran on the first day of strikes. His son Mojtaba Khamenei was chosen on Sunday to succeed him.
Iran is responding to the operation with missile and drone attacks targeting Israel, regional U.S. bases and multiple Gulf nations. Israel is also intensifying its long-running strike campaign against the Iran-backed Hezbollah militia in Lebanon.
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Iran's Education Ministry said Monday that 168 students were killed in an attack on a girls' elementary school in Minab in southern Iran this weekend.
An Israel Defense Forces spokesperson told ABC News on Sunday that Israel doesn't target civilians. "So far we have found no connection to any IDF activity. No IDF activity in that area at all, but we're looking into it," the spokesperson said.
The Israeli Air Force, with the guidance of Israeli intelligence, has begun an additional broad strike on Iranian regime targets in the heart of Tehran, the Israel Defense Forces said.
Defense Secretary Pete Hegseth and Gen. Dan Caine, the chairman of the Joint Chiefs of Staff, are scheduled to hold a press conference at the Pentagon at 8 a.m. ET on Monday to provide details about the campaign against Iran.
The briefing will be the first of any kind by the administration since the start of what the Pentagon is calling "Operation Epic Fury" on Saturday.
-ABC News' Luis Martinez
U.S. Central Command (CENTCOM) said in a Monday statement that three U.S. Air Force F-15E Strike Eagle fighter jets were "mistakenly shot down by Kuwaiti air defenses" while defending against attacks by Iranian aircraft, missiles and drones.
"All six aircrew ejected safely, have been safely recovered and are in stable condition," the CENTCOM statement said. "Kuwait has acknowledged this incident, and we are grateful for the efforts of the Kuwaiti defense forces and their support in this ongoing operation."
"The cause of the incident is under investigation. Additional information will be released as it becomes available," CENTCOM added.
