By Holly Yan and Chelsea J. Carter
(CNN) — Perhaps the only man in the world who can explain why the Boston Marathon bombings took place is sedated with a tube down his throat, unable to speak.
Suspect Dzhokar Tsarnaev was in serious but stable condition at a Boston hospital and cannot talk, Massachusetts Gov. Deval Patrick told reporters.
“I, and I think all of the law enforcement professionals, are hoping for a host of reasons that the suspect survives, because we have a million questions, and those questions need to be answered,” the governor said Saturday.
“There are parts of the investigation, in terms of information and evidence, that still needs to be run to ground.”
As Tsarnaev remains under heavy guard at the hospital, new details have emerged in the case. Here are the latest developments:
The suspect — what’s next?
Authorities have not publicly detailed how Tsarnaev was injured, but a federal official said the teen has injuries to the throat.
An official who has been briefed on the case said the 19-year-old was “intubated and sedated.”
Authorities have not publicly said what charges will be filed against the teen. But a Justice Department official, speaking on condition of anonymity, told CNN the teen will face federal terrorism charges and possibly state murder charges.
Although Massachusetts does not have a death penalty, prosecutors could seek the death penalty at the federal level, the Justice Department official said.
The government has invoked the public safety exception, a designation that allows investigators to question the teen without reading him his Miranda rights and without a lawyer present, said another Justice Department official, also speaking on condition of anonymity.
But the chief of police where Tsarnaev was captured said officers did not question the suspect immediately after he was found.
“There was no interviewing at the scene. He needed aid, and we got him to the hospital,” Watertown Police Chief Edward Deveau said.
After the bombings, Tsarnaev went out to party
As an army of officers hunted for the suspects in Monday’s marathon bombings, Tsarnaev acted like any other college sophomore.
Tsarnaev was on the campus of University of Massachusetts-Dartmouth every day after the attack until late Thursday, a university official told CNN. Tsarnaev attended classes and dorm parties while the rest of Boston came to a tense standstill.
A student at the school told The Boston Globe she saw Tsarnaev Wednesday night at a party that was attended by some of his friends from intramural soccer.
“He was just relaxed,” she said, asking the paper not to print her name.
At the dorm where Tsarnaev lived, students joked Thursday as they viewed the FBI photos on television, a senior who lived in the suspect’s dorm told The Boston Globe.
“We made a joke like, that could be Dzhokar,” Pamala Rolon said. “But then we thought it just couldn’t be him. Dzhokar? Never.”
Tsarnaev ran over his brother in a stolen Mercedes
Tsarnaev and his older brother, Tamerlan Tsarnaev, are accused of setting off two bombs near the finish line of the Boston Marathon on Monday, killing three people and leaving more than 170 wounded.
Soon after the FBI released the suspects’ photos to the public, the brothers killed a Massachusetts Institute of Technology police officer for no obvious reason, officials said. The Tsarnaevs then hijacked a Mercedes, telling the driver they were the marathon bombers, and hurled explosives at the pursuing officers, authorities said.
Handguns, a rifle and at least six bombs — three of which exploded — were found at the scene, Deveau told CNN’s Wolf Blitzer.
“They jump out of the car and unload on our police officer,” Deveau said “They both came out shooting — shooting guns, handguns. He’s under direct fire, very close by.”
The Watertown police chief estimated “there was over 200 shots fired in a five- to 10-minute period.”
Tamerlan Tsarnaev ran out of ammunition during the shootout and was tackled by officers. That’s when the younger Tsarnaev drove the Mercedes toward the officers and his brother.
“They dive out of the way, and he (the younger brother) drives over his brother and drags him a short distance down the street,” Deveau said.
Tamerlan Tsarnaev was later pronounced dead at the hospital. He was wearing explosives and a triggering device when he died, a source briefed on the investigation told CNN.
One of the brothers threw an explosive at the officers. Investigators later discovered it was a pressure cooker bomb, similar to the ones used at the marathon Monday, Deveau said.
The brother: Hints of radicalization
The Tsarnaev family originally hails from the Russian republic of Chechnya and fled the brutal wars there in the 1990s. The two brothers were born in Kyrgyzstan.
An FBI official said agents interviewed Tamerlan Tsarnaev in 2011 at the request of the Russian government. The FBI said Russia claimed he was a follower of radical Islam and a strong believer, and that he had changed drastically since 2010.
Tamerlan Tsarnaev apparently became increasingly radical in the last three or four years, according to an analysis of his social media accounts and the accounts of family members. But so far, there is no evidence of active association with international jihadist groups.
In August 2012, soon after returning from a long visit to Russia, the older Tsarnaev created a YouTube channel with links to a number of videos.
Two videos under a category labeled “Terrorists” were deleted. It’s not clear when or by whom.
But analysis by CNN and the SITE Intelligence Institute has uncovered a screen grab from one of those videos. It features members of the group Imarat Kavkaz — identifiable by the logo on their shirts. Imarat Kavkaz is the most potent militant Islamist group in the north Caucuses — which includes Chechnya and Dagestan.
Separately, a U.S. intelligence source told CNN that investigators are looking into whether Tsarnaev had any connections with the group, known in English as Caucus Emirates. The source says Tsarnaev had several computer links to the group in his social media activities, and investigators are looking into the possibility he may have received “operational plans” from this group.
Imarat Kavkaz has its roots in the 1990s Chechen insurgency. It was founded in 2007 to bring together various Jihadist groups fighting to create an Islamic state in the region.
Its overall leader is Doku Umarov, a veteran Chechen guerrilla who claimed responsibility for the 2011 bombing of Moscow’s international airport.
But so far, evidence suggests that the two brothers acted alone in the bombings and subsequent shootout, Deveau told CNN on Saturday.
“From what I know right now, these two acted together and alone,” the police chief said. “I think we have to be ever vigilant, and we’re learning as we go along, but as far as this little cell — this little group — I think we got our guys.”
CNN’s Tim Lister, Paul Cruickshank, Deborah Feyerick, Pamela Brown, Julian Cummings, Barbara Starr, Ann O’Neill, Melissa Gray, Susan Candiotti, Tom Watkins, Jake Tapper, Shannon Travis and Drew Griffin contributed to this report.