Take this one:
They're point to a bag being held by a totally different guy. Hell, is everyone carrying a bag? And is every one of them holding a bomb? It's the Boston Marathon, a long day. My guess there were a lot of bags in the crowd. The only one that sticks out is this one:
Note how the bag sticks out and seems to have some weight to it.
This link seems to be making a whole lot of projections. People seemed to not be paying attention to the race? It's a 2-3 hour race. Not exactly like watching a hockey game and speaking of which, I've seen plenty of people not paying attention at a hockey game.