Jonathan Shapiro

A friend of Boston Marathon bombing suspect Dzhokhar Tsarnaev is believed to have provided the handgun used to kill a Massachusetts Institute of Technology police officer during the manhunt, people with knowledge of the investigation said Tuesday.

A friend of Boston Marathon bombing suspect Dzhokhar Tsarnaev is believed to have provided the handgun used to kill a Massachusetts Institute of Technology police officer during the manhunt, people with knowledge of the investigation said Tuesday.