The surviving suspect in the Boston Marathon bombings suffered an injury to his throat and may not be able to talk, a federal official told CNN on Saturday, possibly hindering attempts by authorities to question him about a motive in the attack.
With one suspect dead, authorities believe answers to a motive and whether the brothers had help rest with Dzhokar Tsarnaev, who was captured Friday night just minutes after authorities had indicated that a massive manhunt for the suspect appeared to come up empty.
The official, who was briefed on Tsarnaev's condition, spoke on condition of anonymity.
Tsarnaev was in "serious but stable condition" and "not yet able to communicate yet," Massachusetts Gov. Deval Patrick told reporters during an impromptu briefing on Saturday.
Federal prosecutors are at the heavily guarded Beth Israel Deaconess Medical Center, where Tsarnaev is being treated for wounds.
Authorities have not publicly detailed the injuries sustained by the teen, but an official who has been briefed said Tsarnaev has been "intubated and sedated." The official also spoke on condition of anonymity.
"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. There are parts of the investigation, in terms of information and evidence, that still needs to be run to ground," Patrick said.
Authorities have not said whether they have questioned Tsarnaev, nor have they 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.
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, another Justice Department official, also speaking on condition of anonymity, told CNN.
Tsarnaev, 19, and his older brother, 26-year-old 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.
The arrest of Tsarnaev brought to an end a manhunt that paralyzed Cambridge, Watertown and Boston as authorities searched door to door for a suspect not only believed to be behind the bombings, but who they feared also could unleash more explosives.
So far, evidence suggests that the two brothers acted alone in the bombings and subsequent shootout, Watertown Police Chief Edward Deveau said.
"From what I know right now, these two acted together and alone," Deveau told CNN on Saturday. "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."
Even so, questions remain.
"Why did these young men who grew up and studied here as part of our communities and our country resort to such violence? How did they plan and carry out these attacks? And did they receive any help? The families of those killed so senselessly deserve answers," President Barack Obama said Friday in a televised address.
24 hours of chaos
Shortly after the FBI released photos of the suspects Thursday night, Tsarnaev and his older brother led authorities on a wild car chase and shootout.
Officials say the brothers, for no obvious reason, killed Massachusetts Institute of Technology police officer Sean Collier while he was sitting in his car. The Tsarnaevs then hijacked a Mercedes, telling the driver they were the marathon bombers, and hurled explosives at the pursuing officers, authorities said.
"There was an exchange of over 200 rounds of gunfire, there were improvised explosive devices, and handmade hand grenades thrown at the officers at the scene," Boston Police Commissioner Ed Davis said.
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.
The FBI, while executing a search warrant at a residence believed to have been affiliated with Tsarnaev, took three people into custody for questioning Friday. It was unclear Saturday what information the FBI was seeking and whether the three were released.
'Pool of blood'