4 dead after pro-Trump supporters storm Capitol

Police had earlier confirmed the death of one woman who was shot, and D.C. Police Chief Robert Contee further elaborated that she was shot by a plainclothes Capitol Police officer, Anadolu Agency reported.

The woman, who authorities are yet to identify, "was transported to a local hospital where, after all lifesaving efforts failed, she was pronounced deceased," Contee said.

"This is a tragic incident and I send my condolences to the victim’s family and friends," he added.

While the Capitol Police is a separate law enforcement agency than the D.C. police department, the latter will nonetheless launch an internal affairs probe into the shooting as it does for all police-involved shootings in the nation's capital.

Contee said the other three deaths - one female and two males, involved "separate medical emergencies, which resulted in their deaths."

He did not provide any causes of death, saying the determinations will rely upon an examination from D.C.'s chief medical officer.

Meanwhile, at least 14 police officers were injured, including one who was seriously hurt when he was "pulled into a crowd and assaulted," Contee said.

At least 52 people have been arrested, the vast majority of whom -- 47 -- were taken into custody for violating Mayor Muriel Bowser's curfew order, Contee said.

He stressed, however, that the figure would change, saying arrests are ongoing.

Bowser separately said police would be issuing notices for people seen breaching the federal legislature.

Police also recovered a pipe bomb from the Democratic National Committee building and another from the Republican National Committee.

A vehicle discovered on Capitol grounds was also found to have a cooler containing a long gun and molotov cocktails, Contee said.