Police Officer Dies a Day After Sustaining Injuries During Riots at the Capitol Building

An officer with the United States Capitol Police is dead following Wednesday's violent pro-Donald Trump riots in Washington, D.C.

Brian D. Sicknick died at 9:30 p.m. Thursday from injuries he sustained "while physically engaging with protesters" at the riots, USCP said in a statement.

Police said that Sicknick collapsed after returning to his division office and was taken to a hospital, where he later succumbed dead. The Metropolitan Police Department’s Homicide Branch will investigate Sicknick's death along with the USCP and federal partners.

Sicknick joined the USCP in 2008 and had also served in the department's First Responder’s Unit.

"The entire USCP Department expresses its deepest sympathies to Officer Sicknick’s family and friends on their loss, and mourns the loss of a friend and colleague," the USCP said in its statement.

The officer's death marks the fifth fatality in connection to the insurrection, in which Trump supporters stormed the Capitol building and vandalized offices as lawmakers gathered to certify electoral college votes for President-elect Joe Biden's November election win.

Ashli Babbitt, 35, was fatally shot by an officer who was confronting rioters as they stormed into the Capitol building, according to police.

"One capitol police officer discharged his service weapon, striking an adult female. She was transported to a local hospital, where after all life-saving efforts failed, she was pronounced deceased," Metropolitan Police Department Chief Robert J. Contee III said at a press conference on Wednesday night.

"The MPD's internal-affairs division is currently investigating this matter as we investigate all officer-involved deaths in the District of Columbia, including ones from other agencies," Contee continued. "This is a tragic incident, and I send my condolences to the victim's family and friends."

RELATED: Photos of the Aftermath of the Pro-Trump Riots at the U.S. Capitol

Authorities confirmed on Thursday morning that three other people had died from "medical emergencies."

They were identified as Rosanne Boyland, 34, Kevin Greeson, 55, and Benjamin Phillips, 50.

According to the Capitol Police, more than 50 officers from the department and Metropolitan Police Department sustained injuries, while several of them were "hospitalized with serious injuries."

"The violent attack on the U.S. Capitol was unlike any I have ever experienced in my 30 years in law enforcement here in Washington, D.C.," Capitol Police Chief Steven Sund, who resigned from his post on Thursday, said in a previous statement. "Make no mistake – these mass riots were not First Amendment activities; they were criminal riotous behavior."