states, preparations are you should way for the pope s historic trip to america next week and law enforcement calling it the largest security challenge ever, this as we get new information of a teen arrested by the fbi outside of philadelphia for allegedly threatening to launch an isis-inspired assault on pope francis during his tour. jonathan deentz reporting that the teen had possible mental health issues and living in a tent in his family backyard. officials debated whether or not to charge him and since it involved the pope and his online activities overseas they decided to move ahead with that. nbc s keir simmons has more on the security concerns overall. reporter: thomas, the vatican saying that it knows of no credible threat to the pope and confirming today that the plan is for the pope to conduct some of that u.s. tour from an open top jeep but even as the vatican laying out the plans for that