American police on Friday identified two brothers of Chechen origin as the perpetrators of Monday’s bombing of the Boston Marathon that killed three and injured nearly two hundred runners and spectators. It was the deadliest terrorist attack in the mainland United States since September 11, 2001.

The older brother, Tamerlan Tsarnaev, was shot dead early Friday after the two had carjacked a vehicle and been chased by police. The younger suspect, Dzhokhar, was later found and arrested in the suburb of Watertown west of central Boston which had been partly cordoned off by authorities during the day.

“We believe this to be a terrorist,” said Boston’s police commissioner Ed Davis before Dzhokhar was apprehended. “We believe this to be a man who has come here to kill people.”

Police in New Bedford, Massachusetts, sixty miles south of Boston, said three more people had been taken into custody for questioning about the bombings.

Schools in Boston were closed on Friday and public transport services suspended after a university security officer had been killed during the night and a transit policeman was wounded. Police destroyed what they believed to be live ordnance in a number of controlled explosions throughout the morning.

Tamerlan was arrested in 2009 on suspicion of assaulting his then girlfriend yet described himself the following year as “very religious” in an interview with a local photographer and lamented, “There are no values any more. People can’t control themselves.”

Dzhokhar described himself on a social network site as a minority from Russia’s Dagestan province, a largely Muslim area that borders Chechnya. He shared videos of fighters in Syria’s civil war where Sunni Muslims, including religious extremists, are seeking the downfall of secular president Bashar al-Assad as well as links to Islamic web pages and sites promoting Chechen independence.

After the dissolution of the Soviet Union in 1991, Chechnya attained de facto independence in the First Chechen War of 1994-1996.

The Tsarnaev family migrated to Dagestan from Kyrgyzstan after a second war restored Russian federal control over Chechnya in 2000. The Kyrgyz State Committee on National Security said in a statement released on Friday that the Tsarnaevs left the Central Asian country in 2001. School officials in Dagestan told international press that they moved to America in March 2002 where they were eventually nationalized.

Several hundreds of thousands of Chechens were deported to eastern Kyrgyzstan by Joseph Stalin in 1944. Many were allowed to return upon the Soviet leader’s death in 1953.

President Ramzan Akhmadovich Kadyrov of the Chechen Republic, who was installed in 2007 with support from Russian president Vladimir Putin, cautioned in a statement against connecting the Boston bombings with the situation in his state. “They grew up in the United States, their attitudes and beliefs were formed there,” he argued on his social media outlet. “It is necessary to seek the roots of evil in America.”

Kadyrov also expressed his sympathy for the victims of Monday’s bombings.