http://www.washingtonpost.com/politi...6a0_story.html
Neither persons with weapons, or with criminal histories, are supposed to get close to the President. This guy had both, the Secret Service hadn't screened him and didn't know it, and they let him on the elevator with the President. Probably was skipped for scrutiny because he was a contractor with building security at the CDC site being visited.
He attracted SS attention, finally, by acting flaky on the elevator. They questioned him, got a quick database check, and learned of the criminal history. About then his supervisor arrives, and tells the guy he's fired (with contractors, you can do that). So the guy turns over his gun, again surprising the Secret Service.
This would be a 'lapse.'