BOSTON-- The two brothers suspected of bombing the Boston Marathon appear to have been motivated by a radical brand of Islam but do not seem connected to any Muslim terrorist groups, U.S. officials said after interrogating and charging Dzhokhar Tsarnaev with crimes that could bring the death penalty.Tsarnaev, 19, was charged Monday in his hospital room, where he was in serious condition with a gunshot wound to the throat and other injuries suffered during his attempted getaway. His older brother, Tamerlan, 26, died Friday after a fierce gunbattle with police.
Dzhokhar communicated with his interrogators in writing, precluding the type of back-and-forth exchanges often crucial to establishing key facts and meaning, according to officials who cautioned that they were still trying to verify what they were told and are also looking at the suspect's telephone and online communications.
The Massachusetts university student was charged with using and conspiring to use a weapon of mass destruction. He was accused of joining with his brother in setting off the shrapnel-packed pressure-cooker bombs that killed three people and wounded more than 200 a week ago.
The brothers, ethnic Chechens from Russia who had been living in the U.S. for about a decade, practiced Islam.
Two U.S. officials said preliminary evidence from the younger man's interrogation suggests the brothers were motivated by religious extremism but were apparently not involved with Islamic terrorist organizations. The officials spoke on condition of anonymity because they were not authorized to discuss the investigation publicly.
In the criminal complaint outlining the allegations, investigators said Tsarnaev and his brother each placed a knapsack containing a bomb in the crowd near the finish line of the world's most prestigious marathon.
The FBI said surveillance-camera footage showed Dzhokhar manipulating his mobile phone and lifting it to his ear just instants before the two blasts.
After the first blast, a block away from Dzhokhar, "virtually every head turns to the east ... and stares in that direction in apparent bewilderment and alarm," the complaint says. Dzhokhar Tsarnaev, "virtually alone of the individuals in front of the restaurant, appears calm."
He then quickly walked away, leaving a knapsack on the ground; about 10 seconds later, a bomb blew up at the spot where he had been standing, the FBI said.
The FBI did not say whether he was using his cellphone to detonate one or both of the bombs or whether he was talking to someone.
The criminal complaint shed no light on the motive for the attack.
The charges were filed just hours before a memorial service for one of the three people killed in the bombings, 23-year-old Boston University graduate student Lu Lingzi from Shenyang, China, was held at the school and attended by hundreds of people, including Massachusetts Gov. Deval Patrick.
"She's gone but our memories of her are very much alive," said her father, Lu Jun, who spoke in his native tongue and was followed by an English interpreter. "An ancient Chinese saying says every child is actually a little Buddha that helps their parents mature and grow up."
The Obama administration said it had no choice but to prosecute Dzhokhar Tsarnaev in the federal court system. Some politicians had suggested he be tried as an enemy combatant in front of a military tribunal, where defendants are denied some of the usual constitutional protections.
But Tsarnaev is a naturalized U.S. citizen, and under U.S. law, American citizens cannot be tried by military tribunals, White House spokesman Jay Carney said. Carney said that since Sept. 11, 2001, the federal court system has been used to convict and imprison hundreds of terrorists.
The next step in the legal process against Tsarnaev is likely to be an indictment, in which federal prosecutors could add new charges. State prosecutors have said they expect to charge Tsarnaev separately in the killing of a Massachusetts Institute of Technology police officer who was shot in his cruiser Thursday night on the campus in Cambridge.
After Tsarnaev is indicted in the bombing, he will have an arraignment in federal court, when he will be asked to enter a plea.
Under federal law, as a defendant charged with a crime that carries a potential death penalty, he is entitled to at least one lawyer who is knowledgeable about the law in capital cases. Federal Public Defender Miriam Conrad, whose office has been asked to represent Tsarnaev, filed a motion Monday asking that two death penalty lawyers be appointed to represent Tsarnaev, "given the magnitude of this case."
A probable cause hearing _ at which prosecutors will spell out the basics of their case _ was set for May 30. According to a clerk's notes of Monday's proceedings in the hospital, U.S. Magistrate Judge Marianne Bowler indicated she was satisfied that Tsarnaev was "alert and able to respond to the charges."
Tsarnaev did not speak during Monday's proceeding, except to answer "no" when he was asked if he could afford his own lawyer, according to the notes. He nodded when asked if he was able to answer some questions and whether he understood his rights.
Conrad declined to comment when contacted by The Associated Press.
A statement released Monday by Kazakhstan's Ministry of Foreign Affairs bolstered the U.S. officials' comments about seeking details on the suspect's other modes of communication and his associations.
Two foreign nationals arrested Saturday on immigration violations are from the central Asian nation and may have known the suspects, the ministry said. U.S. authorities came across the students while searching for "possible links and contacts," it said.
Officials have not disclosed the names of the nationals, who the ministry said were found to have "violated the U.S. visa regime."
According to the criminal complaint, Dzhokhar Tsarnaev had gunshot wounds to the head, neck, legs and hands when he was captured hiding out in a boat in a backyard in the Boston suburb of Watertown.
The FBI said it searched Tsarnaev's dorm room at the University of Massachusetts-Dartmouth on Sunday and found BBs as well as a white hat and dark jacket that look like those worn by one of the suspected bombers in the surveillance photos the agency released a few days after the attack, according to the affidavit.
The document included a chilling detail of the suspects' flight from Cambridge: one of the brothers _ it wasn't clear which one _ told a carjacking victim during their getaway attempt, "Did you hear about the Boston explosion? I did that."
Shortly after the charges were unveiled, Boston-area residents and many of their well-wishers _ including President Barack Obama at the White House _ observed a moment of silence at 2:49 p.m. _ the moment a week earlier when the bombs exploded.
In addition to that and the memorial for Lu, who was studying statistics at Boston University, a funeral was held Monday at St. Joseph Church for another victim, Krystle Campbell, a 29-year-old restaurant manager who had gone to watch a friend finish the race. Services have not been announced for the third bombing victim, 8-year-old Martin Richard, of Boston.
As of Monday, 51 people remained hospitalized, three of them in critical condition. At least 14 people lost all or part of a limb; three of them lost more than one.
Sullivan reported from Washington. Associated Press writers Steve Peoples, Allen Breed, Bridget Murphy, Jay Lindsay and Bob Salsberg in Boston and Pete Yost in Washington contributed to this report.
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