The Secret Service arrested a shoeless man for tossing firecrackers over a fence at the White House Monday night, just hours after at least one suspect opened fire inside the nearby Navy Yard killing 12 people before he died following a shootout with police.

Although the sounds outside the northwest gate were initially described as sounding like gunshots, a US Secret Service official said it was firecrackers and no gun was found.

Three uniformed Secret Service officers arrested the middle-aged man who had dark hair and wore a blue shirt and white shorts. His white shoes lay on the ground near where an officer tackled him.

The capital has been on high alert following the Navy Yard shootings.

The Associated Press contributed to this report