“His radical turn could very well have happened here,” Dagestani sociologist Zaid Abdulagatov said. “The Islam that we have in Dagestan today is very tough, very politicized, very dark at times.”

As in the cases of other now infamous young men from immigrant backgrounds – like France’s Mohammed Merah, who died in a shootout with police a year ago after killing seven people on a gun rampage in Toulouse – it may be impossible to disentangle the psychological demons from political motives.

“It’s a complicated mix of reasons, usually as much personal as they are transnational or global,” says Rafaello Pantucci, who studies such cases at London’s United Royal Services Institute, a defense and security think tank…

His mother now speaks proudly of his apparent religious awakening, and says she does not believe he would have been capable of the Boston attacks.

“He changed when he started practicing Islam. He would read all the time,” she said. “He had started going to nightclubs, but ever since I said to him that ‘You are a Muslim, you should not do such things, they are haram’, he became more religious,” she told Reuters in English in Makhachkala.

During his stay in Dagestan, relatives say, he clearly stood out as an American, speaking Russian with a foreign accent and slipping into English when he could not remember a word.

“I don’t think he was interested in friendships,” his mother said, adding that he followed lessons online in the Koran to try and understand it in its original Arabic. “He was reading, always in front of the computer – he was taking classes on the Koran,” she said.

“He was very interested. He didn’t want to read it in translation. He said, ‘Mama it’s very difficult, but I want to do this’. He really wanted to get into the true reading of the Koran,” she said. “I was happy about that.”