(CNN) -- Dzhokar Tsarnaev, the surviving suspect in the Boston Marathon bombings, may be charged in his hospital bed Sunday, a Department of Justice official told CNN.
Because Tsarnaev is still in serious condition, a judge would come to his hospital bedside to charge him, a law enforcement source said, noting that suspects who face federal charges are normally arraigned within 48 hours of arrest. Tsarnaev is currently unable to speak.
Authorities have not said publicly what charges will be filed.
A Justice Department official, speaking on condition of anonymity, told CNN he will face federal terrorism charges and possibly state murder charges.
Although Massachusetts does not have the death penalty, prosecutors could seek the death penalty at the federal level, the Justice Department official said.
Lawmaker believes slain suspect trained in Russia
New details emerged Sunday as investigators tried to determine more about the brothers they believe were behind attacks last week that killed three spectators and a police officer.
House Homeland Security Chairman Michael McCaul told CNN that slain suspect Tamerlan Tsarnaev, Dzhokar Tsarnaev's older brother, received training while he was in Russia for six months in 2012.
The Texas Republican also questioned why the FBI did not take further action against Tsarnaev when he was investigated before his trip.
Tsarnaev may have traveled under an alias when he went to Russia, House Intelligence Committee Chairman Rep. Mike Rogers said on CNN's "State of the Union."
Rogers, a Republican from Michigan, also told NBC that Tamerlan Tsarnaev may have become radicalized by Islamic extremists during that trip.
The Russian embassy tweeted Friday that the brothers were not on the consular registry at the embassy in Washington nor the general consulate in New York.
Dzhokar Tsarnaev remains under heavy guard. His brother was killed early Friday as the pair tried to elude police.
The brother: Hints of radicalization
The Tsarnaev family 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 Saturday 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 Caucasus region, 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 that he 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.
Rebels who call themselves Mujahideen of the Caucasus Emirate Province of Dagestan issued a statement Sunday, saying they are not fighting the United States.
"We are at war with Russia," it said. The statement also said that children are never targets of the group.
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."
What's next for the suspect?
Authorities have not publicly detailed how Tsarnaev was injured, but a federal official said the 19-year-old has injuries to the throat.
An official who has been briefed on the case said he was "intubated and sedated."
The government has invoked the public safety exception, a designation that allows investigators to question Tsarnaev without reading him his Miranda rights and without a lawyer present, said another