Social video from the scene shows the U.S. Capitol on lockdown Saturday. The lockdown was placed after a suicide at the West Front of the building, police said. (The Washington Post)

Robert Bishop, a 47-year-old real estate developer from Annapolis, Md., had just snapped a selfie early Saturday afternoon at the West Front of the U.S. Capitol when he heard the pop.

He looked up and saw a woman clasping her hand to her mouth.

“He just shot himself,” she said.

Behind Bishop, a man lay on his side. Nearby, police say, were a roller briefcase, a backpack and a sign. Officers drew their guns and rushed forward.

“He was not moving. He did not move at all,” said Bishop, who was there to meet his daughters to see the cherry blossoms.

The violence shattered a beautiful spring day and threw the Capitol into a nearly three-hour lockdown as authorities pursued the possibility of a broader threat.

Melani Ross, 50, of Alexandria, Va., said she had just walked down from the Capitol when she smelled what she thought was gunpowder. She initially thought “it was just fireworks or something,” but then she saw people running down the steps and children crying.

“It was like a throng,” Ross said.

But officials ruled out any larger plot. “There seems to be no nexus to terrorism or anything related to that,” said U.S. Capitol Police Chief Kim Dine. The East Front of the Capitol reopened just before 4 p.m. But Lt. Kimberly Schneider, spokeswoman for the U.S. Capitol police, said an area near the building’s lower West Terrace will remain “closed until further notice as we continue our investigation.”

The police declined to identify the man until his family could be notified.

Police were also vague about the sign, saying only that it related to “social justice.” Bishop said two others who witnessed the shooting told him that it said, “Tax the one percent,” and that he seemed to raise it just before pulling the trigger.

The shooting caused a few anxious and confusing moments for visitors to the Capitol, which was largely empty with Congress on spring recess.

Jim White was at the Capitol Visitor Center when the announcement of the lockdown came over the loudspeaker. He said there was no panic, just chatter about what could be going on outside. His 1:30 p.m. tour went on as scheduled. The only indication that something was amiss: The tour guide kept stretching and extending his talk.

“We kept asking him, ‘What’s happening?’ and he said he didn’t know,” said White, a 63-year-old IT director for the city of Philadelphia. Finally, having exhausted his commentary, the guide let them go. White and his friend returned to the waiting area, where they immediately checked their phones for updates.

“We read that someone had committed suicide,” he said. “And we understood there was concern that there still may be a bomb.”

So White settled in to wait. He took a seat below the replica of the Statue of Freedom — ironic, he quipped, given his current status.

“I know it’s not a joking matter, but people are getting restless, and they’re wondering why we’re still here,” he said. “We’re just stuck here watching hundreds of other people checking their phones.”

Police cordoned off the area surrounding the Capitol with yellow crime tape — and inside, among several emergency vehicles, was a D.C. hazardous materials truck — but bystanders seemed more curious than scared. One woman on a bicycle stopped to take a selfie with the scene in the background.

Kate Schillinger, 26, said she was in the Library of Congress when a bystander told her that the Capitol was locked down just before 1:15 p.m. She said a security guard told her there was some type of shooter.

Schillinger, who lives in the District and was touring the library with her cousins from North Carolina, said there appeared to be little urgency, though, from bystanders.

One of her cousins, 15-year-old Matt McLaughlin, said he looked out an upstairs window and saw very little amiss.

“Even people, like, next to the Capitol, they didn’t seem panicked at all,” McLaughlin said.

Jay Bernard, 20, who is in the Navy and lives at Fort Meade, came up to the scene about 3:30 p.m. He had been in Alexandria earlier in the day and decided to swing by downtown.

“I was hoping to get a closer look at the Capitol,” he said.

Now? “That’s not going to happen.”

Bernard called the incident “a bit unfortunate,” especially with all the tourists in town to see the cherry blossoms.

“Always something going on here, though,” he said.

Robert Costa and Lori Aratani contributed to this report.