jenna: a possible attack avert averted. a chemistry student arrested for possibly planning a gas attack on the pope's visit. greg burke has this live from rome. >> reporter: every couple of years the pope organizes something called world youth day in a different city. this year it is in madrid. this world's youth day is shaping up a little differently than other ones. one because of a protest this evening, 5,000 people expected. protests against the high cost of the trip. the second thing the arrest of a 24-year-old mexican man apparently arrested because he wanted to break up this protest with some sort of chemical or gas attack. a little excitement before the pope even arrives tomorrow. it looks like the police did not say they actually recovered any memorandum kals, but that the man was making threats online and they are obviously very