The Justice Department says it will spare no resources in investigating the death, and possible murder, of Capitol Police officer Brian D. Sicknick during the riots that took place on Wednesday at the U.S. Capitol building. 

Brian Sicknick, a member of the Capitol Police First Responder's Unit who joined the force in July 2008, was on duty Wednesday when he was injured "while physically engaging with protesters," police said in a statement. The officer collapsed after the attack and was taken to a local hospital, where he died at 9:30 p.m. Thursday.

The Capitol Police said Thursday night that authorities from multiple agencies were investigating Sicknick’s death as a homicide, according to a statement from the Capitol Police.

During a call Friday, DOJ and FBI officials said that they were, "investigating the circumstances" of Officer Sicknick’s death jointly with their law enforcement partners and that it is, "an active investigation."

Capitol Police Officer Brian Sicknick

Capitol Police Officer Brian Sicknick (US Capitol Police)

"Our thoughts and prayers are with the family and fellow officers of U.S. Capitol Police Officer Brian D. Sicknick, who succumbed last night to the injuries he suffered defending the U.S. Capitol, against the violent mob who stormed it on January 6th," Acting Attorney General Jeffrey A. Rosen said in a statement.

"The FBI and Metropolitan Police Department will jointly investigate the case and the Department of Justice will spare no resources in investigating and holding accountable those responsible."

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Fox News correspondent Gillian Turner reported that Sicknick was "hit by a piece of metal" during the struggle. 

"The entire U.S.C.P. 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 force said in a statement.

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Hundreds of police officers and emergency response personnel lined the streets near the Capitol in Washington, D.C., overnight to honor a fallen U.S. Capitol Police officer.

The officers observed a moment of silence around midnight to honor Officer Brian D. Sicknick, the fourth member of the force to die since it was founded nearly 200 years ago, and the fifth death stemming from the riot.

Reporter Mike Valerio of WUSA 9 posted a video of the officers standing by the road around midnight on Thursday, with their car sirens running silently in tribute. Valerio described the display as "stunning."

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Political leaders have also paid tribute to Sicknick, with Speaker Nancy Pelosi ordering flags flown the U.S. Capitol to be flown at half-staff to honor Officer Sicknick. 

"Anytime a member of law enforcement dies in the line of duty it is a solemn reminder to us all that they run toward danger to maintain peace," White House Dep. Press Secretary Judd Deere told Fox News. "The President and the entire Administration extend our prayers to Capitol Police Officer Brian Sicknick’s family as we all grieve the loss of this American hero."

Officials have reported around 50 police officers were injured during the rioting, with Sicknick so far the only death among the police who defended the Capitol and Congress, according to The New York Times.

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Capitol Police reported making 14 arrests during the riot, with local police making dozens of additional arrests, mostly in connection with unlawful entry and violating the city’s curfew on Wednesday night.