A police officer has died from injuries sustained as President Donald Trump’s supporters stormed the Capitol, a violent siege that is forcing hard questions about the defeated president’s remaining days in office and the ability of the Capitol Police to secure the area.

The U.S. Capitol Police said in a statement that Officer Brian D. Sicknick was injured “while physically engaging with protesters” during the Wednesday riot. He is the fifth person to die because of the melee.

The brother of Officer Sicknick released the following statement to ABC News:

“After a day of fighting for his life, he passed away a hero. I would like to thank all of his brothers and sisters in law enforcement for the incredible compassion and support they have shown my family. My family and I hope that our privacy can be respected as we grieve. Thank you.”

The rampage that has shocked the world and left the country on edge forced the resignations of three top Capitol security officials over the failure to stop the breach. It led lawmakers to demand a review of operations and an FBI briefing over what they called a “terrorist attack.” And it is prompting a broader reckoning over Trump’s tenure in office and what comes next for a torn nation.

Protesters were urged by Trump during a rally near the White House earlier Wednesday to head to Capitol Hill, where lawmakers were scheduled to confirm Biden’s presidential victory. The mob swiftly broke through police barriers, smashed windows and paraded through the halls, sending lawmakers into hiding.

One protester, a white woman, was shot to death by Capitol Police, and there were dozens of arrests. Three other people died after “medical emergencies” related to the breach.

Despite Trump’s repeated claims of voter fraud, election officials and his own former attorney general have said there were no problems on a scale that would change the outcome. All the states have certified their results as fair and accurate, by Republican and Democratic officials alike.

Sen. Ben Sasse, R-Neb., said news of the police officer’s death was “gut-wrenching.”

“None of this should have happened,” Sasse said in a statement. “Lord, have mercy.”

Sicknick had returned to his division office after the incident and collapsed, the statement said. He was taken to a local hospital where he died on Thursday.

Two House Democrats on committees overseeing the Capitol police budgets said those responsible need to be held to answer for the “senseless” death.

“We must ensure that the mob who attacked the People’s House and those who instigated them are held fully accountable,” said Rep. Rosa DeLauro, D-Ct., and Rep. Tim Ryan, D-Ohio. in a statement.

Earlier Thursday, House Speaker Nancy Pelosi said any remaining day with the president in power could be “a horror show for America.” Likewise, Senate Democratic leader Chuck Schumer said the attack on the Capitol was “an insurrection against the United States, incited by the president,” and Trump must not stay in office “one day” longer.