(Photo courtesy of Associated press)

CBS News reported that authorities have not found any evidence of ties to major terror organizations, and that evidence indicates that Tsarnaev and his brother were motivated by religion.

Unable to speak due to gunshot wounds to his tongue and throat, Tsarnaev has been cooperatively communicating with officials via writing and head shakes.

The 19-year-old suspect also told authorities that his brother was the driving force behind the plan, and that the two got their instructions on how to make the bombs from the Internet.

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Tsarnaev was charged with using a wagon of mass destruction to kill on Monday, and could face the death penalty if convicted. The White House said he would be tried in a civilian court.

“He will not be treated as an enemy combatant. We will prosecute this terrorist through our civilian system of justice,” White House Press Secretary Jay Carney said.

“Under U.S. law, United States citizens cannot be tried in military commissions. And it is important to remember that since 9/11 we have used the federal court system to convict and incarcerate hundreds of terrorists.”

Tsarnaev was assigned three public defenders and has agreed to "voluntary detention," but declined to answer questions about bail, NBC News reported.

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Some experts worry that the brothers may be connected to other terrorist organizations or militant groups. Tamerlan Tsarnaev visited Russia from January to July of last year, and officials are trying to piece together what the older brother and second suspect of the Boston bombings may have done while he was there.

Gregory McNeal, a professor at Pepperdine University School of Law, told NPR News that there is "some compelling evidence that these guys did not act alone, I can't see the government taking the death penalty off the table."

Many unanswered questions still shroud the case, and authorities are still working to find a motive.

Authorities are trying to figure out where the two suspects got their bomb-making supplies and guns, since neither one had the necessary permits to carry firearms. Tsarnaev could also shed light on what exactly his brother did when he traveled to Russia for six months last year, and if the brothers did have plans and supplies for future attacks.

FBI, Homeland Security and counterterrorism officials will give Congress a classified briefing on the Boston Marathon bombings on Tuesday, said NBC.

A probable cause hearing for Tsarnaev was set for May 30.

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