President Barack Obama was not on the premises at the time of the incident -- the White House said he had gone to play golf at Andrews Air Force Base.
CNN, citing an unnamed law enforcement source, said the suspect approached a security checkpoint, where he drew a weapon.
Secret Service officers shot the man, who was wounded and taken into custody. His condition was not immediately known.
CNN reported that Vice President Joe Biden was at the White House and taken to a secure location during the incident.