NOT TEA PARTIERS. AGAIN. Suspects described as brothers from Chechnya. “The suspects involved in the Boston Marathon bombing were brothers from the Russian Caucasus who moved to Kazakhstan before coming to the United States several years ago, a source briefed on the investigation told CNN.” If they’re Chechens, they’re almost certainly Muslim.

UPDATE: Much more here. Also, from the Boston Herald:

The suspects were identified to The Associated Press as coming from the Russian region near Chechnya, which has been plagued by an Islamic insurgency stemming from separatist wars. A law enforcement intelligence bulletin obtained by the AP identified the surviving bomb suspect as Dzhokhar A. Tsarnaev, a 19-year-old who had been living in Cambridge, just outside Boston, and said he “may be armed and dangerous.”

Two law enforcement officials told the AP that Tsarnaev and the other suspect, who was not immediately identified, had been living legally in the U.S. for at least one year.

State Police Col. Timothy Alben said the slain man was Suspect No. 1 in Monday’s Boston Marathon bombings and the man police are seeking is Suspect No. 2, the man in the white hat seen in images released by the FBI yesterday. The fugitive was described as armed and dangerous, as police set a 20-block perimeter bordered by Arsenal Street and Mount Auburn Avenue. All vehicular traffic has been banned in Watertown.

The entire MBTA system has been shut down.

Stay tuned.

MORE: One Down, One At Large.

Related: “It’s beginning to smell a lot like London and Madrid.”

STILL MORE: Nearly 400,000 people in lock-down as manhunt continues.

Plus: Suspects in marathon bombings are brothers, authorities say.

And several readers comment that there are probably quite a few people in the Watertown area who wish they had a gun right about now.

MORE STILL: Army of Islam? Stay tuned.

Plus: Drones.

Also: Boston, Benghazi, and the “T” Word.

LATEST: Source: Police Investigating Car from Mass. in Niagara Falls. “A police source tells 2 On Your Side that New York State Police have pulled over a vehicle in Niagara Falls allegedly with two Russian nationals in the vehicle. The car was pulled over at 19th and Elmwood in the Falls. Bomb techs and a robot are being used to investigate four suspicious backpacks in the vehicle. Another source tells us the vehicle has Massachusetts license plates.” Probably a false alarm, but who knows?

MORE: Explosions inside home as Boston police hunt second marathon bomb suspect.