Charles Mackay was a Scottish poet, journalist, author, anthologist, novelist, and songwriter, remembered mainly for his book Extraordinary Popular Delusions and the Madness of Crowds. source
Now, we don't get that many specific threats against sporting events, per se. But we know from listening to the chatter how terrorists want to attack iconic events. So whether it's a major Fourth of July celebration or the Super Bowl or the World Series, we assume that that is what they're targeting.