The parents of the two main suspects in the Boston bombings said on Thursday their sons had been framed and accused US authorities of killing the older brother to put on a display.
Anzor Tsarnaev, the father, banged the table in anger as he announced plans to go from Russia to the United States to "find out the truth" and Zubeidat Tsarnaeva, the mother, said she had wanted to scream when she heard of her elder son's death.
She denied Tamerlan Tsarnaev, 26, had made contact with Islamist militants during a stay in Russia last year and said she was considering giving up her US citizenship.
"I wanted to scream to the whole world, 'What did you do?' What have you done with my son? He was alive. Why did you need to kill him? Why didn't you send him to Guantanamo or whatever? Why? Why?," she shouted at a new conference, her voice cracking.
"It is some kind of show, spectacle," she said, adding that she wanted her son buried in Russia, where he has roots.
Wearing a black head scarf, she spoke in accented English as she maintained her belief her sons were victims of a conspiracy.
"Politics is a dirty business. I don't know in whose interest this was. I only know one thing, that my children didn't do this."
She recounted that she had called Tamerlan after the bombing and he had told her not to worry.
He was shot dead by police in a firefight four days after the bombings at the Boston Marathon which killed three people and wounded 264.
His brother Dzhokhar, 19, was captured after a manhunt. He has been charged with crimes that carry a possible death penalty and is now in hospital being treated for his wounds.
Pounding the table with his fists, Anzor Tsarnaev said: "I am going to the United States. I want to say that I am going there to see my son, to bury the older one. I don't have any bad intentions. I don't plan to blow up anything."
"I am not angry at anyone. I want to go find out the truth," said Anzor, his eyes hidden behind dark glasses.
He said he would go as soon as possible but that he had not yet bought a plane ticket.
Influence of ethnic Armenian emigre
Anzor and Zubeidat returned last year to Russia's restive region of Dagestan, where they lived for a little over a year more than a decade ago before emigrating to the United States.
Although the brothers have roots in Dagestan and neighbouring Chechnya, neither had spent much time there until Tamerlan returned last year for six months.
His parents denied he had had any contact with militants fighting to establish an Emirate in the region, saying they kept a watchful eye on him during his stay.
They said, however, that Tamerlan had frequented a mosque which is considered by local police to be a hotbed of radical Islamist ideas.
Investigators are looking into whether Tamerlan was influenced by the local Islamist militants, who are waging an insurgency against Russian rule of the North Caucasus.
Zubeidat was questioned for almost seven hours by Russia's security services on Wednesday on her son's movements during his time in Dagestan.
On another occasion, when the FBI came to question Tsarnaev in the United States in 2011, Zubeidat said they had quizzed her about his religious views.
"They told me, 'Don't you think that Tamerlan is being a little extreme about religion? Do you think he would think about organising something, some kind of ... terrorism?," she said.
Despite the visit, she said: "I really did not see any reason for worry."
Anzor and Zubeidat said Tamerlan had been influenced by an ethnic Armenian emigre from Azerbaijan whom they knew only by the name of Misha.
"Tamerlan very much respected him for him knowing Islam... He was (saying) like, 'Mom, look at him, he prays, he is fasting all the time'," said Zubeidat, who describes herself as a devout Muslim and said she was inspired to become more religious by the man called Misha.
The family said they had met the man in the Russian-speaking diaspora in Boston in 2007.
US officials have said Tamerlan became more radical from around 2009.
"I wasn't praying until he (Misha) prayed in our house, so I just got really ashamed that I am not praying, being a Muslim, being born a Muslim ... while Misha, who converted, was praying," Zubeidat said.
"When he used to come to our house, there was nothing not to like about him. (He) was very nice, very gentle," she said.