A U.S. Secret Service officer shot a man with a gun who approached a checkpoint outside the White House on Friday, May 20 afternoon and refused to drop his weapon, the Secret Service said, according to the Associated Press.

The White House was briefly placed on a security alert after the shooting, which happened within view of sightseers as sidewalks were crowded with families, school groups and government workers.

The armed man approached the checkpoint on E Street shortly after 3 p.m., and ignored repeated orders from the officer to drop his gun, according to a statement from David Iacovetti, a Secret Service deputy assistant director.

The officer fired one shot at the man and the gun was recovered at the scene, Iacovetti said. The man was transported in critical condition to a nearby hospital, an emergency medical services spokesman said, according to AP.

President Barack Obama was away playing golf, but Vice President Joe Biden was in the White House complex and was secured during the lockdown, his office said. The security alert was lifted about an hour later.

The gunman never made it inside the White House complex, and no one else was injured, the Secret Service said.