“We initially thought it was inside the stadium,” he said. “It was pure panic right away.”
Some people crouched under their seats, while Mr. DeAngeles said he jumped the turnstiles with his friend and girlfriend and then made it onto the street and back home, as police cars converged on the area.
“It’s just wild,” he said. “You don’t think you will be in that experience, but you hear ‘active shooter’ and just run.”
Nick Butler, 28, said he had been sitting in the stands beyond center field and had been watching the weather, wondering if the game would be rained out. When he saw fans behind home plate sprinting, he assumed the rain had arrived, but then he noticed that some were ducking and the players were not in the dugouts.
Mr. Butler said he leapt up from his seat and headed to the center field concourse, looking for an exit, turned a corner and was told by a staff member that he could not leave that way. Then he saw “a stampede of people running in our direction.”
That’s when he realized, “something’s happening here.”
He said he turned and ran and found his way into what he described as a Nationals operations center, where he ducked under tables and waited until a public announcement made it clear that fans could leave.
“I am comforted in some way that we were never really in danger,” he said.
After fans poured of the ballpark, the metro platform at the Navy Yard station was crowded, as it typically is after a game, but the fans were quieter than usual, with many people sharing their recollections of what they had heard.
Amy Fiscus and David Waldstein contributed reporting.