Hi, I'm new here. I left my intro on the newbies forum.
I've been to the Boston Marathon many times as a spectator, watching a family member in the race. I saw that some posters were speculating that the runners must have been stopped well in advance. I agree.
I've seen a lot of people on the internet writing that the explosion occurred hours after the top finishers. This is true. However, many are also assuming or implying that few runners were left. That's not true. The marathon starts in "waves". The elite women started at 9:32 (50 runners). Elite men and "wave one" at 10:00 (9,000 runners). Wave 2 at 10:20 (9,000 runners). Wave 3 at 10:40 (9,000 runners). It's staggered by runner speed. Faster runners are in the earlier waves. If you started in wave 1, 2:49 EST was at the 4:49 mark for the marathon running time. If you started in wave 2, it would have been 4:29 into your race. If you started in wave three, 2:49 EST was at 4:09 race clock time.
The elite women, elite men, and wave one all should have been finished by 2:49 EST, so forget them. Waves two and three still had a lot of runners in the race at 2:49 EST. Although I said it would have been 4:09 race clock time for wave three, that's not entirely true. The runners' official time gets calculated by the microchip they wear. Their individual race time doesn't start until they cross the starting line. If you were in wave three and you didn't reach the starting line until, say, 11:00, even though the runners in the front of the pack started at 10:40 (it often takes that long, the runners are densely packed and very backed up at the starting line), your real race clock time at 2:49 EST would have been 3:49... same situation, but wave 2, it would have been 4:09 race clock time.
So, at 2:49 EST, the runners at/near the finish could have been anywhere between 3:49 (estimated) and 4:29 race finishing time. If you look at average finishing times, overall http://www.runtri.com/2012/01/average-m ... 00-to.html
and by age group http://www.runtri.com/2012/01/marathon- ... n-new.html
, from past Boston Marathons, you'll see there should have been a LOT of runners near the finishing line on Boylston. It's not just the stragglers. That's the most densely packed finishing time period. Take note: there are over 27,000 runners officially in the race!
We had "live video" of the first blast. Nobody would have been able to stop all those runners. The super cops/first responders wouldn't have been able to run down Boylston Street, opposite direction of the runners, without getting trampled or colliding. It's not like all the runners would have come to a screeching halt just because there's a little white smoke contained to the sidewalk area. If they had, there would be photos of a massive pack of piled up runners just before the finish line. Or there should be photos of lots of runners who continued to the end while all of this was happening.