Trump inauguration live updates: Highlights from Trump's inaugural speech and swearing in

Rep. Ilhan Omar, D-Minn. sent out a blistering X post criticizing fellow Democrats who called Trump a threat to democracy and are now "willing to be there and clap for him."

"People are more upset at performers/artists attending Trump's inaugural events but not upset at all the politicians who told them he was a 'threat to democracy' going to these events are not serious," she wrote.

"Performers at least know they are there to perform and get paid, but these politicians who ran their mouth for 4 yrs and are now willing to be there and clap for him, that's who they should be mad at," she added. "They lied to you and your criticism/anger should be rightfully directed at them.

Former President Bill Clinton and former Secretary of State Hillary Clinton, who lost the 2016 election to President-elect Donald Trump, have arrived at Trump's second inauguration. Trump supporters gathered at Capital One Arena in Washington, D.C., booed as the Clintons walked in.

Former President George W. Bush and former first lady Laura Bush are also at the Capitol, along with former President Barack Obama, who is attending the inauguration without former first lady Michelle Obama.

Former Vice President Mike Pence was also not accompanied by his wife, Karen Pence.

Hundreds of people are gathered inside the Capitol Rotunda, including several of Trump's Cabinet picks: Tulsi Gabbard, tapped for director of national intelligence; Robert F. Kennedy Jr., chosen to lead Health and Human Services; and Pete Hegseth, his pick to lead the Pentagon.

His pick for secretary of state, Marco Rubio, could be confirmed as soon as Monday night. Rubio is considered one of Trump's least controversial picks.

A number of Senate committees that will vote on different nominees have scheduled meetings for later this week.

With a sea of red hats and the campaign soundtrack blasting, Capital One Arena emulates the environment of a campaign rally.

Notably, a desk sits at the end of the stage across the podium. Trump is expected to sign executive orders from here.

There is a feed of Trump's movements being streamed live on the Jumbotrons as well. As the president-elect departed St. John's church, the crowd here burst into applause and chanted "USA."

There were also chants of "JD-48" as they watched the vice president-elect and his wife arrived at the White House.

ABC News Senior Political Correspondent Rachel Scott spoke to one couple from Alabama who arrived at 2:30 a.m. and said there were still "thousands" of people ahead of them.

EMS first responders from Butler, Pennsylvania -- the site of that first assassination attempt -- are expected to be present as well.

-- ABC News' Rachel Scott and Benjamin Siegel