Three people were taken into custody, D.C. Metro Police Chief Cathy Lanier said, and the weapon was recovered.
The incident began when officers, who were at 4th St. SW and P St. SW, about 2 miles south of the Capitol, saw someone they thought they had a lookout alert on, Lanier said. The car fled the area.
While officers chased the car, one suspect extended an arm out the window with a gun and fired a shot toward the police behind the car, Lanier said.
After the suspect fired, the shooter dropped the gun in a tunnel near the Capitol, Lanier said.
The chase ended near the Capitol building at 1st and D St.
While police were restricting movement in and out of the complex, the brief lockdown did not restrict movement inside the Capitol.
The lockdown was ordered after reports of shots fired at Metropolitan Police Department officers. No civilians or law enforcement officers were injured in the incident.