(CNN) -- Dzhokhar Tsarnaev, the surviving suspect in the Boston Marathon bombings, may be charged by federal prosecutors as early as Sunday, a Department of Justice official told CNN.
Because Tsarnaev is still in serious condition, a judge or magistrate would likely come to the hospital to inform him of the charges, a law enforcement source said. An arraignment would take place at a later date.
Tsarnaev, 19, is currently unable to speak and is under heavy guard.
Tsarnaev was arrested Friday morning when, after 25 minutes of negotiations with the FBI, he crawled out of the boat he was hiding in and surrendered, a law enforcement official with knowledge of how the arrest occurred told CNN.
Authorities have not said publicly what charges will be filed against him, but 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 capital punishment at the federal level, the Justice Department official said.
"Given the facts that I've seen, it would be appropriate to use the death penalty in this case and I hope they would apply it in federal court," Sen. Chuck Schumer, D-New York, said Sunday on CNN's "State of the Union."
Boston Mayor Thomas Menino and Gov. Deval Patrick announced the planned moment on Sunday.
The silence will be followed by the ringing of bells.
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 near the race's finish line and their alleged involvement in the death of a police officer.
House Homeland Security Chairman Michael McCaul said on CNN's "State of the Union" that slain suspect Tamerlan Tsarnaev, Dzhokhar 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 Tamerlan Tsarnaev when he was investigated before his trip.
"There were concerns about this individual. And yet when he travels abroad and gets to a very dangerous part of the world, nothing seems to be done," he told CNN.
McCaul said after his final Sunday talk show appearance that he thought Tamerlan Tsarnaev may have made other trips to the region. The congressman said Tsarnaev was "starting to radicalize" several years before the six-month trip.
"It's unconfirmed at this point. ... My judgment is we'll probably see there were other trips to the region," McCaul said.
Tsarnaev, 26, may have traveled under an alias when he went to Russia in 2012, House Intelligence Committee Chairman Rep. Mike Rogers said Sunday.
Rogers, R-Michigan, also told NBC that Tamerlan Tsarnaev may have become radicalized by Islamic extremists during that trip. The elder Tsarnaev died after a shootout with police early Friday.
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.
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, authorities said.
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.
But U.S. official and a law enforcement source said Sunday the Russian government's request was vague. The lack of specifics limited the amount the FBI was able to investigate Tamerlan, the law enforcement official said.
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 his visit to Russia, the elder 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, Doku Umarov, is 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, Watertown Police Chief Edward Deveau told CNN 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 Dzhokhar 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 in the case, a designation that allows investigators to question Tsarnaev without reading him his Miranda rights and without a lawyer present, said another Justice Department official, also speaking on condition of anonymity.
Secretary of Defense Chuck Hagel told reporters on a flight to Israel that the attack was "criminal," adding that "every region of the world is not safe from these terrible acts."
He also said he has not seen any intelligence that linked the brothers to any terrorist organization, but it was still early in the investigation.
Deveau, the Watertown police chief, said officers did not question the suspect immediately after he was found.
In another development, immigration agents arrested two people Saturday in New Bedford, Massachusetts, on visa issues, according to a statement from Immigration and Customs Enforcement. A law enforcement official said the two were detained as authorities investigated their possible involvement in the bombings case. It was determined they weren't involved, that official said, but they were arrested on administrative immigration violations, according to the ICE statement.
After the bombings, Tsarnaev went out to party
As an army of officers hunted for the suspects in Monday's marathon bombings, Dzhokhar Tsarnaev acted like any other college sophomore.
He 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 much of Boston was at a tense standstill.
"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 of the bombing suspects on television, a senior who lived in that dorm told The Boston Globe.
"We made a joke like, that could be Dzhokhar," Pamala Rolon said. "But then we thought it just couldn't be him. Dzhokhar? Never."
The campus, which was closed during the search for the bombing suspects, reopened Sunday morning.