WASHINGTON (AP) — Slain U.S. Capitol Police Officer Brian Sicknick lay in honor Wednesday in the building he died defending, as colleagues, members of Congress and the president and vice president paid their respects.

Sicknick died after defending the Capitol on Jan. 6 against the mob that stormed the building and interrupted the electoral count after then-President Donald Trump urged supporters on the National Mall to “fight like hell” to overturn his defeat. The U.S. Capitol Police said in a statement that Sicknick, who died the next day, was injured “while physically engaging with protesters,” though the cause of his death has not been determined.

President Joe Biden traveled to the Capitol to pay tribute to Sicknick shortly after the viewing began Tuesday night, briefly placing his hand on the urn in the center of the Capitol Rotunda, saying a prayer and sadly shaking his head as he observed a memorial wreath nearby. He was accompanied by first lady Jill Biden. House Speaker Nancy Pelosi, Senate Majority Leader Chuck Schumer and a handful of other congressional leaders also paid their respects.

Vice President Kamala Harris and her husband, Doug Emhoff, paid their respects Wednesday, placing their hands over their hearts and then touching the urn. A steady stream of lawmakers and police officers made its way through the Rotunda. Michigan Rep. Dan Kildee, one of several Democrats who were caught in the upper gallery of the House chamber while the rioters banged on the doors, wiped away tears.

Dozens of Capitol Police stood at attention as Sicknick's urn was carried up the Capitol steps Tuesday night. It was the first time an urn, rather than a casket, has been part of a memorial observance in the Capitol Rotunda.

There was a viewing period for his Capitol Police colleagues overnight, and lawmakers were to pay tribute at a ceremony Wednesday morning. A ceremonial departure for Arlington National Cemetery was planned later in the day.

Members of Congress remain shaken by the riots and are grappling with what it means not only for the future of the country but for their own security as elected representatives. While lawmakers were united in denouncing the riots, and Trump’s role in them, the parties are now largely split on how to move forward.

The attack led to uncertainty, fear and political turmoil in Congress as Biden began his presidency. House Democrats impeached Trump a week after the attack, sending a charge of “incitement of insurrection” to the Senate, where Republicans are unlikely to provide the votes necessary to convict him. At the same time, the building has been cut off from the public, surrounded by large metal fences and defended by the National Guard.

Sicknick, 42, of South River, New Jersey, enlisted in the National Guard six months after graduating high school in 1997, then deployed to Saudi Arabia and later Kyrgyzstan. He joined the Capitol Police in 2008. Like many of his fellow officers, he often worked security in the Capitol itself and was known to lawmakers, staff and others who passed through the building’s doors each morning.

There are still questions about his death, which was one of five as a result of the rioting. As the mob forced its way in, Sicknick was hit in the head with a fire extinguisher, two law enforcement officials said. He collapsed later on, was hospitalized and died. The officials could not discuss the ongoing investigation publicly and spoke to The Associated Press on the condition of anonymity.

Investigators are also examining whether he may have ingested a chemical substance during the riot that may have contributed to his death, the officials said.

Biden's tribute Tuesday evening stood in stark contrast to Trump, who never made a public expression of sorrow over the officer's death or took any responsibility for the attack.

Pelosi and Schumer announced last week that Sicknick would lie in honor, saying his heroism “helped save lives, defend the temple of our democracy and ensure that the Congress was not diverted from our duty to the Constitution.”

His sacrifice, they said, “reminds us every day of our obligation to our country and to the people we serve.”

Pelosi said in a letter to colleagues on Tuesday that the Capitol Police “demonstrated extraordinary valor” on Jan. 6 and urged members to pay their respects to Sicknick. She has also encouraged members to take advantage of trauma resources available to congressional employees.

She said protecting the Capitol and the lawmakers who work there is a “highest priority” and that there will be a need for extra money to do so. During the assault, many of the insurrectionists called out for members, including Pelosi. They also targeted Vice President Mike Pence, who was in the building to preside over the electoral count.

“The insurrectionist attack on January 6 was not only an attack on the Capitol, but was a traumatic assault targeting Members,” she said.

Senate Minority Leader Mitch McConnell, speaking on the Senate floor Wednesday, said that Sicknick “gave our nation the last full measure of devotion,” referencing Abraham Lincoln's Gettysburg Address during the Civil War.

“Four weeks ago, the Rotunda was strewn with the debris of an insurrectionist mob,” McConnell said. “Today, it is adorned in solemn thanksgiving for the sacrifice of a hero.”

Sicknick is only the fifth person to lie in honor in the Capitol Rotunda, a designation for those who are not elected officials, judges or military leaders. The others who have lain in honor were John Gibson and Jacob Chestnut, Jr., two officers who were killed in a 1998 shooting at the Capitol; civil rights leader Rosa Parks, who died in 2005; and the Rev. Billy Graham, who died in 2018.

___

Associated Press writers Michael Balsamo, Colleen Long and Darlene Superville contributed to this report.