Tamerlan Tsarnaev, 26, died after a shootout with police early Friday. Dzhokhar Tsarnaev was captured that night, after police found him hiding in a boat in the back yard of a house in the Boston suburb of Watertown, Massachusetts.
Older suspect's wife
With one suspect dead and the other hindered in his ability to communicate, investigators are eager to speak to Tamerlan Tsarnaev's wife, Katherine Russell, to see what she might know about incidents leading up to the bombings.
On Monday, her attorney said she learned of her husband's alleged involvement through news accounts.
"She knew nothing about it at any time," Amato DeLuca said in response to questions about whether Russell knew of plans to attack the marathon.
Tsarnaev stayed home and cared for the couple's 2-year-old daughter while his wife worked long hours as a home-care aide, according to DeLuca.
The family is devastated, the attorney said.
"They're very distraught. They're upset. Their lives have been unalterably changed. They're upset because of what happened, the people that were injured, that were killed. It's an awful, terrible thing," he said. "And of course (for) Katy, it's even worse because what she lost -- her husband and the father of her daughter."
Clues about 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; Dzhokhar became a U.S. citizen in 2012, while Tamerlan was a legal U.S. resident.
An FBI official said agents interviewed Tamerlan Tsarnaev in 2011 at the request of the Russian government. The FBI said Russia claimed that he was a follower of radical Islam and that he had changed drastically since 2010.
But the Russian government's request was vague, a U.S. official and a law enforcement source said Sunday. The lack of specifics limited how much the FBI was able to investigate Tamerlan, the law enforcement official said.
In August 2012, soon after returning from a visit to Russia, the elder Tsarnaev brother 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.
Tamerlan Tsarnaev attended prayers periodically at the Islamic Society of Boston's mosque in Cambridge, a board member told CNN's Brian Todd. In a statement issued Monday, the society said he twice interrupted sermons -- once in November to express his opposition to celebrating any holiday as un-Islamic, and once in January when he tore into the preacher for citing civil rights leader Martin Luther King.
The second time, the congregation shouted back, "Leave now," the statement said.
"After the sermon and the congregational prayer ended, a few volunteer leaders of the mosque sat down with the older suspect and gave him a clear choice: either he stops interrupting sermons and remains silent or he would not be welcomed," it said. "While he continued to attend some of the congregational prayers after the January incident, he neither interrupted another sermon nor did he cause any other disturbances."
Tamerlan Tsarnaev "began coming intermittently to our congregational prayers on Friday over a year ago and occasionally to our daily prayers," the statement read. "The younger suspect was rarely seen at the center, coming only occasionally for prayer."
Memorials and tributes
One of the victims, Krystle Campbell was memorialized Monday morning in a service at St. Joseph Catholic Church in Medford, Massachusetts. After the service, police officers lined the street in front of the church as other officers wearing dress uniforms saluted as the casket bearing her remains was taken from the church and loaded into a hearse.
Another memorial service was scheduled Monday night at Boston University for Lingzi Lu, a student from China. Lu was a graduate student in mathematics and statistics. Before coming to Boston, she won an academic scholarship to the Beijing Institute of Technology, where she received accolades for her math skills.
On Wednesday, Vice President Joe Biden will attend the memorial service for MIT police officer Sean Collier, who was allegedly killed by the Tsarnaev brothers.
A week after the marathon bombings, 50 people remain hospitalized, including two in critical condition, according to a CNN tally.
At least a dozen survivors have endured amputations.
Patients at Boston Medical Center have received visits from war veterans who have also suffered amputations. The vets, Dr. Jeffrey Kalish said, told patients that their lives aren't over because they've lost limbs.
"We've seen really tremendous success and great attitudes," he said.