WASHINGTON — Police and federal agents swarmed into a northwest Washington neighborhood on Friday after at least four people were shot in a flurry of gunfire. City officials warned people to stay inside because of an "active threat" as dozens of officers in tactical gear searched for the suspect.

The law enforcement officers responded to the scene near Connecticut Avenue and Van Ness St. in the Van Ness neighborhood of Washington shortly before 3:30 p.m. The gunfire rocked the normally quiet neighborhood that's home to several schools and colleges and dozens of embassies.

Hours later, the Metropolitan Police Department said investigators were seeking to question a 23-year-old man from Virginia they identified as a person of interest. The man was "linked to social media postings" that emerged as part of the investigation, Assistant Police Chief Stuart Emerman said.

The victims included a 54-year-old man, a woman in her 30s, a woman in her mid-60s who was grazed in the back by a bullet, and a 12-year-old girl who was shot in the arm, Emerman said. All of the victims were expected to recover. Police warned people who live in the nearby neighborhoods of Cleveland Park and Van Ness to shelter in place for hours.

The gunfire erupted just as parents were picking up their children from the Edmund Burke School, a private college preparatory school, sending frantic parents running from the scene and putting Burke and other nearby schools on immediate lockdown.

Bibi Stewart of Anne Arundel, Maryland, was approaching the line to pick up her 12-year-old twins when she heard the gunfire ring out. She said it sounded like the shots were coming from above and at a distance.

"They did it right at dismissal," she said.

Stewart said she saw glass shattering in a bridge connecting different wings of the school and she saw the tires of cars in the pickup line shot out.

"They're just saying they're OK" and hiding in the school with their friends and adults, she said of her children.

Police in tactical gear were seen escorting people — including college students from nearby campuses — out of apartment buildings in the area. Officers pointed their rifles upward toward other buildings and windows as the people moved quickly down the street with their hands raised above their heads.

"I had to look in parents' eyes tonight who are terrified ... thinking of what might happen to their children," District of Columbia Mayor Muriel Bowser said at a news conference. "And we have experienced this too much in our country. The epidemic of gun violence, the easy access to weapons, has got to stop. People should not be scared taking their children to school."

Police were going door-to-door in area buildings as they searched for the shooter.

Emerman said police were also aware of a video posted online that may be connected to the shooting, though he cautioned that investigators hadn't yet authenticated the video. Police were questioning witnesses at the scene and were still trying to discern a motive for the shooting, he said.

Video posted on Twitter captured the sound of bursts of rapid gunfire.

The University of the District of Columbia, which is located nearby, went into lockdown, telling students and staff to shelter and stay in place. In a tweet, the college said there was an "active shooting incident near student housing" and the suspect remained at large.

Eduardo Bugay, a student at the college, said he was in his first-floor apartment in the AVA building when he heard the shots.

"At first I was confused," he said, not sure what he was hearing. Then, he said, he got scared.

Bugay said the university sent emails telling students to stay in place. About 30 to 40 minutes after he first heard the gunshots, police came knocking on his door to escort him and others from the building.

A slew of law enforcement officials and emergency crews were sent to the scene. Agents from the FBI arrived in an armored vehicle and the U.S. Secret Service said its officers were aiding police in the search and at the scene. The Bureau of Alcohol, Tobacco, Firearms and Explosives said its agents were also assisting in the investigation.

Separately on Friday, emergency medical crews were called to the U.S. Supreme Court around 6:30 p.m. after a man attempted to set himself on fire outside the building. The man was rushed by police helicopter to a local hospital and his condition wasn't immediately known.