A day after three people were killed and over 130 injured by two bombings at the Boston Marathon, the search for answers is well underway.
This morning, President Obama addressed the nation:
"Clearly we are at the beginning of our investigation. It will take time to follow every lead and determine what happened, but we will find out."
No arrests have been made at this point. The FBI has taken charge of the investigation and is appealing for any video, audio and still images taken by spectators.
But sifting through all the submissions in an organized fashion presents a significant challenge.
"Videos could be coming from everywhere, they could be coming in a multitude of formats. In order to maintian the kind of evidentiary chain, you need to pin down a lot of details," says Alexis Madrigal, senior editor at The Atlantic, who wrote an article about forensic video analysis of this sort yesterday on the publication's website.
During a press conference yesterday, Massachusetts Governor Deval Patrick urged the public to be patient as the investigation unfolds:
"There will be a heightened law enforcement presence consistent with the severity and seriousness of the ongoing investigation. People should expect -- those who are riding the T -- that there will be random checks of backpacks and other parcels. We just ask everyone to be patient with that inconvenience for the time being. It is for the public's safety."
Laura Perille, executive director of the educational philanthropic organization Edvestors, says her first priority was making sure her coworkers, a few of whom were near the explosions, were safe.
"We did what any family does, check on eachother. We used email and text," she says. "Most of the team are feeling the way most residents of Boston are feeling -- really absorbing the dimensions of the tragedy, compassion for the victims, respect for the heroism of the first responders."
The area around Copley Square remained closed Tuesday morning, as did exit ramps from major highways leading to the area. People may return to work today, though city officials are urging those who can work from home to do so and to avoid the city as investigators continue to scour the area for evidence.
"It's very important that we move forward in our day to day lives and not be paralyzed by fear," says Karen DiMartino, who works for Palladium Group which decided not to suspend their strategy conference today. "We need to move forward, we need to show a productive positive attitude."
Immediately following yesterday’s explosions, many in the Boston area were having trouble making cell calls. Cell phone companies denied reports their systems had been shut down as a precaution. Officials say the problem had to do with bandwidth -- the ability of the telecommunications system to handle the crush of calls.
"What we understand from looking at disasters like Katrina, or Sandy or some of the tsunami disasters it that the best way to keep communications going in a crisis is to have redundancy and diversity of services, so that at least some of the services will be operating, you hope, when others fail," says Daniel Weitzner, principal research scientist at MIT's CSAIL program.
The Red Cross set up a place for family members and loved ones to connect. Google has also stepped in to help family and friends of Boston Marathon runners find their loved ones after explosions near the finish line. The site, called Google Person Finder, allows users to enter the name of a person they're looking for or enter information about someone who is there. Authorities are asking the public to call in tips at 1-800-CALL-FBI (1-800-225-5324).
The Associated Press contributed to this report. This article was updated at 1:45 pm EST to include a quote from President Obama.