BOSTON — Vice President Joe Biden on Wednesday 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 an outdoor service for slain Massachusetts Institute of Technology police officer Sean Collier, Biden explicitly connected the bombings and Collier’s slaying to the U.S. war against terrorists worldwide. Preceded by a martial keen of bagpipes, 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.

“They know they can never defeat us,” Biden said, adding that “it infuriates them that we refuse to bend, refuse to change, refuse to yield to fear.”

Investigators believe Collier was gunned down in his police car around 10 p.m. 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 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 Friday after a late-night shootout in which, police say, 200 bullets were fired and several explosive devices were thrown.

Additional state charges relating to Collier’s death and the wounding of Massachusetts Bay Transit Authority police officer Richard Donohue could come soon.

“We have an active investigation,” Stephanie Chelf Guyotte, spokeswoman for Middlesex County District Attorney Marian T. Ryan, said in a telephone interview Wednesday, “and we do expect to file charges.”

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 Tuesday in the state House of Representatives, though in a roundabout way that let lawmakers avoid a politically difficult up-or-down vote.

Across the Charles River, in downtown Boston, Tsarnaev also could theoretically face additional state murder charges for the three individuals killed in the April 15 bombings. For now, though, the Suffolk County district attorney who handles Boston cases is letting federal prosecutors take the lead.

“We have a team of prosecutors in place, if there is some change,” Jake Wark, spokesman for Suffolk County District Attorney Daniel F. Conley said in an interview Wednesday, “but the district attorney believes that the federal statutes give federal authorities appropriate jurisdiction.”

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 Wednesday that “some personnel . . . headed down” from the U.S. Embassy in Moscow to the Russian province of Dagestan, a largely Muslim region about 1,200 miles away, to talk to the parents of the Tsarnaev brothers.

In Washington, other investigators trekked to a secure underground Capitol Hill facility late Wednesday to brief members of the House Permanent Select Committee on Intelligence on the latest findings.

Rep. C.A. “Dutch” Ruppersberger, D-Md., the ranking Democrat on the House Select Intelligence Committee, said lawmakers were told that remote-control devices, the type used in toy cars, were
used to detonate the bombs.

“The indication I got it was remote control,” he said. “That says to me that you need some sort of sophistication to use that device to set off bombs.”

The Boston street where both bombs had been planted along the marathon route opened Wednesday to the public for the first time since the April 15 explosions. As relieved residents strolled Boylston Street, businesses were beginning to reopen, many sporting “Boston Strong” signs in their front windows.

Public works crews were repairing brick sidewalks that had been damaged by the blast, and orange traffic cones were placed to cordon off the actual bomb sites, as crews laid fresh concrete over them. Several bouquets of flowers and rose petals were left at the scene.