Got back from Boston last night. I had crossed the finish line about 50 minutes before the blasts and was well clear. I was far enough away that I didn't hear anything, but did hear sirens afterward as I was trying to find the bar a bunch of us were meeting at. My first thought is that there might be a runner in cardiac arrest being rushed to the hospital. Got to the bar and within a couple minutes people started hearing the news via twitter, then on TV. The mood instantly changed from the post-race high and sharing stories to shock and anger, and concern with people we hadn't seen yet. Eventually all were accounted for of both my online and local friends. One friend cross the finish about 30 seconds before the blast and turned and saw the stands emptying and people in disarray, though not in total panic. A few others got caught where they stopped and diverted people about 1/2 mile from the finish.
One friend heard someone in his hotel say that he was in the stands and saw someone run out and drop a bag along the side of the course and run away and very shortly later the explosion happened. That doesn't sound too likely given the other reports, but I'd hate to think someone is so pathetic that they'd make up a story like that for attention or whatever. In any case my friend did pass along that info to the FBI, though as a second hand story it didn't get jumped on as key information. Other than that, I was limited to the same information and conflicting stories that you all were. I have no insight to offer on domestic vs. international terrorist.
We stayed in the bar for quite awhile because it was in a basement and seemed safe, plus the police wanted people off the streets, and for awhile we didn't know the JFK thing wasn't related, so we didn't know if there was more coming. When I finally did walk the 3-4 blocks to my hotel, it was pretty eerie at how few people and cars were out, except for a lot of law enforcement and some fire trucks out, all with lights going, and some sirens. Helicopters overhead too. Someone else had heavy duty SWAT trucks at the entrance and checking everyone going in very carefully. It was like the next thing you expected to see was Jack Bauer hopping out of a black SUV. My hotel just required me to show my key to get in the building.
Yesterday things were getting back to somewhat normal except at the blast area, which was blocked off and had news trucks from all over parked just outside the barricades. I went to Cambridge as I had originally planned to tour Harvard and MIT, and thought maybe getting out of the middle of Boston wasn't a bad idea. I got lots of nods and smiles as I went around in my marathon jacket and shirt, and a few people stopped to talk with me. One was nearly in tears, one was very angry, most were just resolved not to let this ruin everything, and told me they hoped I'd come back. Unfortunately I didn't run fast enough to re-qualify, but if I do again, I'll be back. I didn't hear anyone who said this would keep them away. In fact one friend had told us before the race that this would be his last Boston and perhaps his last marathon, and afterward he said F it, I'm coming back in 2014.
The other thing about yesterday is that there were national guard all over the subways, and police cars and beat cops everywhere. And while you expect to hear sirens in the city, when I'd hear them, especially fire trucks, I got that sick feeling in my stomach that more bad had happened. Fortunately it didn't, but I was happy when my delayed flight finally took off.