The two men suspected in the Boston Marathon bombings were armed with a small arsenal of guns, ammunition and explosives when they first confronted the police early Friday, and were most likely planning more attacks, the authorities said Sunday.
United States officials said they were increasingly certain that the two suspects had acted on their own, but were looking for any hints that someone had trained or inspired them. The F.B.I. is broadening its global investigation in search of a motive and pressing the Russian government for more details about a Russian request to the F.B.I. in 2011 about one of the suspects’ possible links to extremist groups, a senior United States official said Sunday.
New details about the suspects, their alleged plot and the widening inquiry emerged on Sunday, including the types of weapons that were used and the bomb design’s link to a terrorist manual. Lawmakers also accused the F.B.I. of an intelligence failure, questioning whether the bureau had responded forcefully enough to Russia’s warnings.