@Setanta,
Understood! Though I live in Sarasota now, I so identify with the area. For 12 yr, I used to go watch the Marathon at Boylston St and/or go to Patriot's Day Red Sawx game. I used to live in Watertown and shop at the Arsenal Mall. this hits so close to home for me. My deepest sympathy to all the victims families and neighbors. Hell, all Americans are suffering these wounds. All innocent people no matter where they live are suffering for the victims and families.
In an odd sort of way, we're at war. No one will admit it or declare it. Terrorist acts such as this (or mass killers depending on you're POV), put us in a wartime dynamic...until they're caught.
Who's to say there still aren't sleeper cells? We have no idea of the motivation or affiliation. We might never learn that.