A timeline of key incidents reported at the White House since 1995:
_ Nov. 11, 2011: U.S. Park Police respond to report of shots fired near the White House. Four days later, the Secret Service says it found evidence the White House was struck by two bullets, although the two incidents have not been conclusively linked.
_ June 2009: A person jumps fence onto White House property and is taken in custody. President Barack Obama is inside the building at the time.
_ Feb. 2001: Secret Service patrol reports man firing shots, waving handgun at southernmost point of the White House fence; requests backup from other authorities, including U.S. Park Police. Office fires a single shot at the gunman's knee, subduing him.
_ June 1998: Immigration officials arrest two Mexican nationals trying to get on White House grounds using false alien registration cards.
_ December 1995: A Texas man is arrested near the White House with a rifle in his car.
_ May 1995: A Virginia man is shot on the White House lawn after scaling a fence with an unloaded gun. Officials said the man had a history of mental problems and may have acted on a suicidal impulse.
Associated Press researcher Judith Ausuebel in New York contributed to this report.