In an ill-timed moment, Rep. Lauren Boebert, R-Colo., shouted at the president, blaming him for the deaths of the 13 U.S. servicemembers killed in an attack at the Kabul airport in Afghanistan last summer, as Biden spoke about veterans exposed to burn pits developing "cancer that would put them in a flag-draped coffin."

"You put them in, 13 of them!" she yelled.

But her words came out just as the president was about to mention the death of his son, Beau Biden, an Iraq War veteran who died from brain cancer in 2015.

"I know," Biden began, attempting to reference Beau. But before he could get the sentence out Boebert shouted.

The members in the chamber immediately booed her.

"One of those soldiers was my son, Major Beau Biden," the president continued. "I don’t know for sure if the burn pit that he lived near, that his hooch was near in Iraq and earlier than that, in Kosovo is the cause of his brain cancer, the diseases of so many other troops. But I am committed to finding out everything we can."

Boebert later addressed the moment on Twitter, saying, “When Biden said flag draped coffins I couldn't stay silent. I told him directly he did it. He put 13 in there. Our heroic servicemen and women deserve so much better.”

-ABC News' Mariam Khan

Biden took a few moments to thank retiring Supreme Court Justice Stephen Breyer for his service on the bench and asked the justice to stand and be recognized.

Breyer has been one of the most loyal attendees of State of the Union addresses over the past 20 years -- and tonight he was clearly touched by the presidential tribute.

Biden then immediately pivoted to his nomination of Judge Ketanji Brown Jackson to fill that seat.

“Since she’s been nominated, she’s received a broad range of support," Biden said.

-ABC News' Devin Dwyer and Justin Gomez

On the pandemic, Biden outlined four "common-sense" steps the U.S. is taking to "move forward safely":

1. Vaccines and treatments: "We will never give up on vaccinating more Americans," Biden said. He also discussed progress on anti-viral treatments and announced a “test to treat” initiative for COVID-positive Americans to obtain Pfizer pills free of charge.

He also announced that starting next week Americans would be able to order even more free rapid tests at .

2. Preparing for new variants: Biden said instead of months or years, we'll be able to deploy new vaccines "within 100 days."

3. Ending shutdowns: Biden stressed the importance of people working in offices safely and keeping schools open. "The vast majority of federal workers will once again work in person. Our schools are open. Let’s keep it that way," he said.

4. Vaccinating the world: Biden said the U.S. has so far sent 475 million vaccine doses worldwide, "and we won't stop."

Sen. Joe Manchin, ., sat with Sen. Mitt Romney, R-Utah, and Republicans during the State of the Union.

“Senator Manchin sat with his colleague Senator Romney to remind the American people and the world that bipartisanship works and is alive and well in the U.S. Senate,” Samantha Runyon, a spokeswoman for Manchin, told ABC News in a statement.

Manchin, who opposed many of President Biden's proposals including the original version of his Build Back Better plan, was seen applauding during several moments when the president outlined his agenda.

-ABC News' Mary Bruce and Trish Turner

Ahead Biden's first State of the Union address, House Republicans claimed the "state of our union is in a crisis," which they say is directly caused by Biden and House Democrats' "failed far-left socialist agenda."

"Tonight, President Biden will try to rewrite history of the past year and pass the buck instead of taking responsibility for the failures of his radical far-left Democrat agenda," the third-ranking House Republican Rep. Elise Stefanik said at a press briefing Tuesday.

Republicans are holding Biden personally responsible for several issues, from inflation to high gas prices to supply chain issues to the invasion of Ukraine.

"The war on Ukraine represents one of the greatest foreign policy failures in modern history," Stefanik said. "For months, President Biden failed to engage in meaningful deterrence against Russian aggression."

Ukrainian-American Rep. Victoria Spartz gave an emotional plea calling for the Biden administration to do more to help Ukraine.

"This is not a war, this is a genocide of the Ukrainian people," Spartz, who represents Indiana, told reporters. "They want to be free people. They want to be with the West."

-ABC News' Mariam Khan