All four people were taken to hospital with potentially life-threatening injuries.
The exact cause of their injuries is still under investigation, officials said.
The lightning was triggered by a severe thunderstorm that swept the entire area shortly before 7 p.m. The National Weather Service issued a severe thunderstorm warning for much of the Beltway from 6:30 to 7:15 p.m. up to 60 mph and quarter size hail.
Chris Vagasky, Vaisala, running a national lightning network, said in a message that there was a “6-beat flash that hit the same spot on the ground” outside the White House at 6:49 p.m. He explained that this means that six separate surges of electricity hit the same point on the ground in half a second. .
A series of storms with frequent lightning swept through the region Thursday night after temperatures soared into the mid-to-upper 90s earlier in the day, prompting heat reports. Heat indexes, a measure of how hot it feels in relation to humidity, were in the 100s to 110s.
The heat-driven storms produced wind gusts of up to 58 mph at Reagan National Airport and downed trees in Winchester, D.C. and Baltimore. The rip currents also led to numerous reports of flooded roads around Baltimore.
Lightning kills 23 people a year in the United States nine dead until now in 2022
This is a developing story and will be updated.