The shooting happened near the intersection of Second and C streets SW.
U.S. Capitol Police said that at about 5 a.m., a lookout for a man with a gun was broadcast over the USCP radio. A few moments later, the suspect was seen pointing a weapon directly at Capitol Police officers, officials said.
Fearing for their lives, officers shot the man.
The suspect was taken to an area hospital. He was said to be in grave condition.
No other injuries were reported. MPD is assisting with the ongoing investigation.
Senate Sergeant at Arms Terrance Gainer, who is responsible for maintaining security in the Capitol, said in a statement that the man had a loaded, semiautomatic handgun and had parked his car near where he was shot, the Associated Press reported.
Second Street was closed between Washington Avenue and C Street in Southwest until the crime scene was processed and the area was deemed clear.