[Obama_Is_Sabotaging_America]

Well, the second bomb is delayed to hit those who exit the building maybe? What building was that second bomb in front of? Might be a lead or clue.. There MUST be surveillance video of the person or persons who placed those backpacks there.

I would look closely at the location of the second bomb and why that spot was chosen. Could be more significant than the first bomb.

[Cicero]

If the two bombs went off twelve seconds apart, that might indicate that the timers were meant to set them off at the same time.

The finish line and just before the finish line would likely be the most crowded spots.

[Just another Joe]

I would look closely at the location of the second bomb and why that spot was chosen.

I would hazard a guess that the second explosion, being about 1 to 2 blocks down the street, was set there to catch anyone running away from the first explosion near the finish line.

There would be many more people on that side of the finish line than on the other side of the finish line.
12 seconds is enough, especially in this day and age, for most people not in the radius of the first blast to be moving away from the first and be caught in the second.

[glorgau]

I’m sure there is software available to stitch together all the disparate videos taken at the scene. This is the kind of stuff that game designers do all day long.

[Andy'smom]

Lennox Hotel.