One of the civilians was a man, and the other a woman.
It appeared from preliminary accounts that the first shooting occurred near the 3900 block of Martin Luther King Jr Ave SE just before 4:30 p.m.
In a tweet police said a man was seen fleeing the area in a car.
Meanwhile, according to police spokeswoman Alaina Gertz, emergency personnel were sent to the area to treat the shooting victim.
At that point, Gertz said, the attacker in the first shooting apparently returned. Both the second civilian victim and the firefighter were then shot, according to a preliminary account from Gertz. Police listed the site of that portion of the incident as the 3900 block of South Capitol Street SW. The address is a stone’s throw from the address listed for the shooting of the first victim.
Gertz said she was not certain whether the first person who was shot was the male or the female victim.
The wounded firefighter was a man, according to D.C. fire and EMS spokesman Vito Maggiolo. He said the firefighter was released from a hospital last night after treatment.
King Avenue and South Capitol Street intersect in the vicinity of the shootings.
No motive was known for the attacks, and as of Sunday evening, no arrest was reported.