Boston bomb suspects 'knockoff jihadists' Vice President Joe Biden has denounced the Chechen brothers accused of planting the Boston Marathon bombs as "two twisted, perverted, cowardly knockoff jihadists," even as investigators scrambled to find out more about the suspects, one living and one dead. Speaking at a service for slain Massachusetts Institute of Technology police officer Sean Collier on Wednesday, Biden explicitly connected the bombings and Collier's slaying to the US war against terrorists worldwide. Biden praised Collier as a "remarkable son (and) a remarkable brother," while his voice rose against those suspected of killing the 27-year-old officer. Investigators believe Collier was gunned down in his police car around 10pm on Thursday by one of the two brothers three days after the marathon bombings. Federal prosecutors have charged Dzhokhar Tsarnaev with use of a weapon of mass destruction and destruction of private property with an explosive for the April 15 bombings in which three people died and more than 260 were injured. Both federal charges carry the potential for the death penalty or for life in prison. Officials reported on Wednesday that the 19-year-old Tsarnaev remains in fair condition at Beth Israel Deaconess Medical Center, where he's being treated for multiple wounds incurred amid several gun battles with police. Tsarnaev's 26-year-old brother Tamerlan died on Friday after a late-night shootout in which, police say, 200 bullets were fired and several explosive devices were thrown. Massachusetts does not allow for the death penalty, and the state last executed a convicted criminal in 1947. A short-lived effort to reinstate the penalty failed on Tuesday in the state House of Representatives, though in a roundabout way that let legislators avoid a politically difficult up-or-down vote. Through a multi-agency Joint Terrorism Task Force, investigators have been continuing to track the Tsarnaev brothers' footprints worldwide. State Department spokesman Patrick Ventrell said on Wednesday that "some personnel ... headed down" from the US embassy in Moscow to the Russian province of Dagestan, a largely Muslim region about 1931km away, to talk to the parents of the Tsarnaev brothers. In Washington, other investigators trekked to a secure underground Capitol Hill facility late on Wednesday to brief members of the House Permanent Select Committee on Intelligence on the latest findings. The bombs apparently were triggered by a remote-controlled detonator, US officials told the Associated Press on Wednesday. One of the anonymous officials told the AP that the detonator was "close-controlled" - meaning it had to be triggered within several blocks of the bombs. An FBI affidavit made public states that videotape shows on the suspects "manipulating" his mobile phone shortly before the blasts.