The North Tower's rooftop, unlike the South Tower, is closed to visitors due to the radio mast and the distinct lack of a fence or observation deck. The only way to access it is via either maintenance doors and stairs on floor 110 or another maintenance stairwell in Windows Really High Up on floor 107. He apparently booked a reservation at WRHU, and stood up, walked to the rooftop access door in the restaurant, and picked the lock. He then managed to climb all of the stairs and unlock the chains that led up there.
He is now standing on the edge of the tower and yelling he is going to jump