Much of last night's action took place in Cambridge and Watertown, a western suburb of Boston.
Boston area residents and business owners are being asked to "shelter in place" during this morning's manhunt. But what does that look like?
All transit has been suspended; residents urged to remain in their homes. Police are conducting a door-to-door manhunt for second bombing suspect.
Makeshift memorials from around the city.
There are millions of men and women wandering around America who spent the best years of their lives in this city.
Notes of sympathy from Kabul, Afghanistan.
Shortly after Monday's bombings, cellular networks collapsed. The same thing happens every time there is a crisis in a large city.
Done right, they might enable "meaningful social interaction" between a neighborhood's new arrivals and its existing residents.
The bombings have turned all the cues and surroundings of this time of year upside down.
The city of Boston is blanketed with security cameras. But finding the right shots is a little like looking for a needle in a hay stack.
Participants in the 2013 Boston Marathon hailed from across the globe.
Early reports suggest at least one of the bombs used in yesterday's Boston Marathon attack was hidden in a garbage can. There's a case to be made for removing them all.
Locals on social media report a distinct lack of chaos, "just a feeling that everyone is focused."
New York, Los Angeles, and Washington, D.C. have stepped up police presence on transit, at tourist attractions, and near hotels.
If there's an uplifting lesson from Boston, it may be the many people who will overcome the trauma of tragedy.
Race officials are reviewing security precautions with local police after the attacks in Boston Monday.
This is more true than ever in the digital age.
Modern-day militia activists have attempted to hold rallies on this holiday in recent years.
Though cell service is spotty, social media is connecting family members and friends.