Reportedly...
Stephen Silva possessed a Ruger P95 with the serial # filed off (a federal offense). He lent his illegal weapon to his friend, Boston Bomber "Dzhokhar Tsarnaev, who told him he wanted it to rob college students in Rhode Island."
That weapon was used to murder Massachusetts Institute of Technology police officer Sean Collier three days after the bombing as Tsarnaev and his brother fled police.
Silva was arrested on drug and firearm charges in July last year, has been in custody since, pled guilty to the charges against him and fully cooperated with the prosecution against Tsarnaev, who was convicted (for both the bombings and the murder of Collier) and sentenced to death.
Today "U.S. District Judge Mark Wolf sentenced Stephen Silva...to time served plus three years' supervised release for the charges that he pleaded guilty to last year."
That's right: 17 months served, 3 years probation, and Silva is free to continue his life as if nothing happened at all.
The very best "gun-control" measures which can be enacted are making sure criminals who are such blatant accessories to murder as this serve the rest of their lives confined.
Evidently, the progressive federal government does not agree, even as it falls all over its politically-correct self trying so desperately to convince its lemmings that it cares, it really, really cares.