CBS News correspondent Bob Orr reports that Tsarnaev is cooperating with authorities, who have not found any evidence of ties to major terror organizations. Injured from a gunshot wound to the neck that has rendered him unable to speak, he is communicating via writing.
Two officials also told The Associated Press that evidence indicated he and the second suspect, his brother, were motivated by religion.
On Monday Tsarneav was indicted with using a weapon of mass destruction to kill, and he could face the death penalty if convicted. A magistrate judge went to the hospital to conduct the initial appearance, an official at the Federal Courthouse in Boston confirmed to CBS News.
"I find that the defendant is alert, mentally competent and lucid," the magistrate judge said in a statement. "He is aware of the nature of the proceedings."
Tsarnaev, 19, was accused by federal prosecutors of joining with his older brother to set off the two pressure-cooker bombs that sprayed shrapnel into the crowd at the finish line last Monday, killing three people and wounding more than 180.
The criminal complaint containing the charges shed no light on the motive for the attack.
Tsarnaev was listed in serious but stable condition at Beth Israel Deaconess Medical Center, unable to speak because of a gunshot wound to the throat.However, Tsarnaev is conscious and responding in writing to authorities, CBS News correspondent Bob Orr reported. Officials did not reveal further details on what they are asking, or what his responses are.
His brother, Tamerlan, 26, died last week in a fierce gunbattle with police.
"Although our investigation is ongoing, today's charges bring a successful end to a tragic week for the city of Boston and for our country," Attorney General Eric Holder said in a statement.
The charges carry the death penalty or a prison sentence of up to life.
"He has what's coming to him," a wounded Kaitlynn Cates said from her hospital room. She was at the finish line when the first blast knocked her off her feet, and she suffered an injury to her lower leg.
In outlining the evidence against him in court papers, the FBI said Tsarnaev was seen on surveillance cameras putting a knapsack down on the ground near the site of the second blast and then manipulating a cellphone and lifting it to his ear.
After the first explosion went off about a block down the street and spread fear through the crowd, Tsarnaev -- unlike nearly everyone around him -- looked calm and quickly walked away, the FBI said. Just 10 seconds or so later, the second blast occurred where he left the knapsack, the FBI said.
The FBI did not make it clear whether authorities believe he used his cellphone to detonate one or both of the bombs or whether he was talking to someone.
The court papers also said that during the long night of crime Thursday and Friday that led to the older brother's death and the younger one's capture, one of the Tsarnaev brothers told a carjacking victim: "Did you hear about the Boston explosion? I did that."
The brothers are ethnic Chechens from Russia who have lived in the U.S. for about a decade. Investigators are focusing on a trip the older brother made last year to Chechnya and Dagestan, in a region of Russia that has become a hotbed of separatist politics and Islamic extremism.
Tsarnaev was charged with using and conspiring to use a weapon of mass destruction against persons and property, resulting in death. He is also likely to face state charges in connection with the shooting death of an MIT police officer.
The Obama administration said it had no choice but to prosecute 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 U.S. 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 9/11, the federal court system has been used to convict and imprison hundreds of terrorists.
U.S. officials said the elite interrogation team would question Tsarnaev, a Massachusetts college student, without reading him his Miranda rights, which guarantees the right to remain silent and the right to an attorney.
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Senior correspondent John Miller told "CBS This Morning" that investigators are focused at the moment on the "public safety exceptions" -- questioning the suspect on matters of immediate threats."It's basically, 'Where did you make the bombs? Are there any more explosives out there? Any more cells? Are there any more people?'" said Miller.
"And while I'm told he's being cooperative, I'm also getting the sense -- and I want to be careful of too many specifics here -- that he's not saying there's a whole second wave of plots or plotters here. Still there are places where there may be explosives and other things to find, it sounds like."
But Miller stressed that is it is still early in the investigation, and the process of questioning Tsarnaev -- who can only respond by writing - is slow. "Things could develop or change," Miller said.
American Civil Liberties Union Executive Director Anthony Romero said the legal exception applies only when there is a continued threat to public safety and is "not an open-ended exception" to the Miranda rule.
In its criminal complaint, 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 one of the suspected bombers in the surveillance photos the FBI released a few days after the attack.
Seven days after the bombings, meanwhile, Boston was bustling Monday, with runners hitting the pavement, children walking to school and enough cars clogging the streets to make the morning commute feel almost back to normal.Residents paused in the afternoon to observe a moment of silence at 2:50 p.m., the time of the first blast. Church bells tolled across the city and state in tribute to the victims.
Also, hundreds of family and friends packed a church in Medford for the funeral of bombing victim Krystle Campbell, a 29-year-old restaurant worker. A memorial service was scheduled for Monday night at Boston University for 23-year-old Lu Lingzi, a graduate student from China.
Fifty-seven victims remained hospitalized Monday, two of them in critical condition. Seventeen patients underwent amputations.
At the Snowden International School on Newbury Street, a high school set just a block from the bombing site, jittery parents dropped off children as teachers -- some of whom had run in the race -- greeted each other with hugs.
Carlotta Martin of Boston said that leaving her kids at school has been the hardest part of getting back to normal.
"We're right in the middle of things," Martin said outside the school as her children, 17-year-old twins and a 15-year-old, walked in, glancing at the police barricades a few yards from the school's front door.
"I'm nervous. Hopefully, this stuff is over," she continued. "I told my daughter to text me so I know everything's OK."
Tsarnaev was captured Friday night after an intense all-day manhunt that brought the Boston area to a near-standstill. He was cornered and seized, wounded and bloody, after he was discovered hiding in a tarp-covered boat in a Watertown backyard.
"We have reason to believe, based upon the evidence that was found at that scene -- the explosions, the explosive ordnance that was unexploded and the firepower that they had -- that they were going to attack other individuals," Davis said. "That's my belief at this point."
Meanwhile, investigators in the Boston suburb of Waltham are looking into whether there are links between Tamerlan Tsarnaev and an unsolved 2011 slaying. Tsarnaev was a friend of one of three men found dead in an apartment with their necks slit and their bodies reportedly covered with marijuana.