As the 79-year-old pope made his way to greet a boy in a wheelchair, one of the many pilgrims behind the boy pulled the pope's arm, causing him to fall over the disabled youth.

Security personnel immediately helped him up as the pilgrim continued to latch onto him. Visibly concerned for the young boy in the wheelchair he leaned against, the pope emphatically scolded the young pilgrim, saying: "Pero que te pasa? No seas egoista! No seas egoista!" ("What is the matter? Don't be selfish! Don't be selfish!")

The scene, which was witnessed by thousands watching the event, prompted organizers to plead with pilgrims to show some restraint.

"Please contain yourself," the announcer said. "Pope Francis wants to greet us, but if we pile up, it will be difficult to do so."

Later, the Vatican spokesman, Jesuit Father Federico Lombardi, said, "It was a very human, very normal reaction" to a situation that was potentially dangerous and one that came near the end of a long day.