The following is coming directly from Boston Police:

Suspicious Package Detonated; Suspect Arrested
At about 9:50 AM on Friday, December 4, 2015, officers from District A-1 (Downtown) responded to a radio call for a suspicious package in the area of 408 Atlantic Avenue, along the Greenway. Upon arrival, officers were informed that a suspicious male had dropped a suitcase by the rear tire of a marked Department of Homeland Security vehicle then left the area in a hurry. The BPD Explosive Ordinance Unit responded, conducted an investigation of the object, and then performed a controlled detonation of the suitcase using a ‘pack bot.’ The officers deemed there to be no additional threat to the public. James Derepentigny, 50, of Lawrence was later arrested with placing the package. Watch the package being detonated:
https://twitter.com/AndreaWBZ/status/672820680946266112/video/1
More recent crime reports in the neighborhood:
Breaking & Entering – Commercial
12/03/15 ~ 6:40am
Fleet Street dry cleaners reports that the front glass door was shattered and an unknown person removed money from the cash drawer.
Aggravated Assault & Battery
12/04/15 ~ 1:54am
Male victim reports that he was inside a Prince Street bakery placing an order, when a male suspect accused him of trying to pickpocket him. At this time, the suspect followed him to in front of his Margaret Street residence and began punching and kicking him. Victim received facial injuries but refused medical attention at this time.
The suspicious package suspect was arrested.
Thanks Joyce. We updated the post.