First pardoned Jan. 6 rioters released in DC

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

According to the presidential inauguration committee, here is what will happen when Trump gets to the Capitol:

First, he will be sworn in around noon.

After, Trump will bid farewell to President Joe Biden and Vice President Kamala Harris. Biden is leaving the Capitol via helicopter to go to Joint Base Andrews, where he will hold a farewell event with his staff.

Trump will then visit the overflow crowd gathered at Emancipation Hall to watch the swearing in and later participate in a ceremony in the presidents signing room. He will eventually return to Emancipation Hall for a review of the troops.