A Capitol Police officer who suffered injuries during Wednesday's riot on Capitol Hill died on Thursday, CNN reported. Brian D. Sicknick died around 9:30 p.m. ET Thursday "due to injuries sustained while on-duty," prompting prosecutors to open a federal murder investigation, Capitol Police officials said.

"Officer Sicknick was responding to the riots on Wednesday, Jan. 6, 2021, at the U.S. Capitol and was injured while physically engaging with protesters," police stated. "He returned to his division office and collapsed. He was taken to a local hospital where he succumbed to his injuries."

Sicknick, who joined the Capitol Police in 2008, was serving in the department's First Responders 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," Capitol Police said.

The details of Sicknick's injuries are unclear, but a video from a local reporter showed that the officer was in the vicinity when rioters discharged a fire extinguisher outside the Senate chamber, The New York Times reported.

Four other people also died during the chaos in Washington, D.C., on Wednesday, including a rioter who was shot and killed by an officer in the building, as well as three people who died after experiencing medical emergencies.

As Blavity previously reported, the chaos started on Wednesday morning when supporters of President Donald Trump stormed the Capitol hoping to disrupt the certification of the 2020 presidential election as it was in the final hours of being finalized to make President-elect Joe Biden the official winner.

The Trump mob forced its way to the Senate floor after punching and tackling police while breaking windows. Vice President Mike Pence, who was performing his role in counting the Electoral College votes, had to evacuate along with the rest of the officials in the building.

"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 said, according to CNN. "Maintaining public safety in an open environment — specifically for First Amendment activities — has long been a challenge." 

Sund, who resigned after the chaos, said officers were "actively attacked" with metal pipes and other weapons.

"They were determined to enter into the Capitol Building by causing great damage," Sund added.

Lawmakers from both parties said they are determined to find out how security allowed a violent mob to invade the building. As Blavity previously reported, dozens of people have been also expressing their outrage on social media, noting the irony of police failing to stop the violence at the Capitol Building after forcing strict measures against Black Lives Matter protesters last year.