When the Boston Marathon bombing was announced on March 15, 2015, the nation was shocked.
But what exactly was happening?
Why was a bombing in a crowded city?
What was the motive behind the attack?
As the news was spreading around the world, the FBI and U.K. government quickly started to piece together the story, and the details of what happened at the Boston marathon were finally emerging.
In the days that followed, the Boston Globe, The Associated Press, the BBC, The New York Times, CNN, MSNBC, The Washington Post, The Hill, ABC News, CBS News, NBC News, ABC and CNN, along with numerous other news organizations, reported on the story.
In response to this coverage, we asked the Boston police and FBI to respond to our questions.
The FBI responded to the first question with a written response.
But then, two days later, the bureau issued a second statement.
The Boston Police Department also provided a second response to our request.
It provided a lengthy and incomplete statement, which you can read below.
Why was the Boston bombing so deadly?
The FBI and Massachusetts State Police had a goal of getting as many details about the attack as possible before it took place.
This goal was complicated by the fact that the bombings were occurring on a busy day in Boston, and that a number of businesses were closed and some public transportation systems were shut down.
A large crowd of people was present in the Boston Convention Center, where the marathon was to begin.
The crowd was estimated at approximately 1,000 people.
The event was to start at 6:30 p.m. local time (7:30 a.m., ET) and finish at 6 p.