Once the president got off, the elevator operator decided to follow him and take pictures. Now, if you were a Secret Service agent and noticed the shifty elevator guy stalking the president, you'd probably tackle him, break his phone and the hand that held it, and immediately order your fellow officers to surround the president and ensure his safety, right? Well, no, you wouldn't do that, because you're in the Secret Service and you are shockingly irresponsible. They actually just let the guy take picture after picture of their boss, presumably because he was just so excited to do it. Normal people don't tell children there's no Santa Claus; these guys don't tell weirdos with cellphones not to Instagram the president.
House Of Representatives
Yes, Virginia, there is a flattering filter.
Upon returning to his elevator and realizing he had nobody to elevate, he returned for yet another photo session, in case he hadn't properly captured Obama's good side. FINALLY, a Secret Service member realized this guy shouldn't be there and kicked him out. But, even then, they didn't know about the gun until later, when the guy's boss learned of what had happened and ordered the man to turn in his weapon.
At this point, the Secret Service had only one skin-saving option left: Don't tell the president. And they even fucked that up -- director Julia Pierson insisted, in sworn testimony, that she briefed the president "100 percent of the time" after a security breach and that she had briefed the president about only one security breach that year (but didn't mentioned the elevator story). Hours later, the media mentioned the elevator story. This is why Julia Pierson has lots of free time lately.