By Scott Malone


BOSTON (Reuters) - A grand jury has indicted accused Boston Marathon bomber Dzhokhar Tsarnaev on charges of killing four people and using a weapon of mass destruction, federal prosecutors in Boston said on Thursday.

Tsarnaev, 19, is one of two ethnic Chechen brothers accused of carrying out the April 15 attack, which killed three people. A fourth victim, a university police officer, died in a gunfight with the pair four days later as authorities raced to capture them.

The younger Tsarnaev, who was badly injured in that gun battle, has been held in a prison hospital west of Boston since his capture on April 19.

(Reporting by Scott Malone; Editing by Gerald E. McCormick)