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 after a shootout just minutes after authorities had indicated that a massive manhunt for the 19-year-old 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 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.

“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 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 massive manhunt that paralyzed Cambridge, Watertown and Boston as authorities searched for a suspect not only believed to be behind the bombings, but who they feared also could unleash more explosives.

Acting alone?

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.

Read more: CNN