Anzor Tsarnaev spoke with The Associated Press by telephone from the southern Russian republic of Dagestan after police said one of his sons, 26-year-old Tamerlan, had been killed in a shootout and the other, Dzhokhar, was being intensely pursued.
"My son is a true angel," the elder Tsarnaev said. He said his son was "an intelligent boy" who was studying medicine.
"We expected him to come on holidays here," he said.
"They were set up, they were set up!" he exclaimed. "I saw it on television; they killed my older son Tamerlan."
Tsarnaev, badly agitated, gave little more information and ended the call angrily, saying, "Leave me alone, my son's been killed."
The younger Tsarnaev gave few clues as to his inner life on his profile on Vkontakte, a Russian equivalent of Facebook, though he did include websites about Islam among his favorites.
The family's origins are in Chechnya, the mostly Muslim Russian republic where separatist rebels fought two full-scale wars with Russian forces since 1994.
A spokesman for Chechnya's leader said the family left Chechnya long ago and went to Central Asia, then moved to Dagestan, a Muslim republic adjacent to Chechnya that has been the site of a sporadic insurgency for more than a decade.
Dzhokhar Tsarnaev attended School No. 1 in Makhachkala, the capital of Dagestan. The principal's secretary at School No. 1, Irina Bandurina, told the AP that Tsarnaev left for the U.S. in March 2002.