The Globe talked to several acquaintances of the Tsarnaevs who talked about how Tamerlan felt plagued by the voices.
From The Globe:
"[The voice] came to him at unexpected times, an internal rambling that he alone could hear. Alarmed, he confided to his mother that the voice 'felt like two people inside of me.'
As he got older, the voice became more authoritative, its bidding more insistent. Tamerlan confided in a close friend that the voice had begun to issue orders and to require him to perform certain acts, though he never told his friend specifically what those acts were.
'He was torn between those two people,' said Donald Larking, 67, who attended the mosque with Tamerlan for nearly two years. 'He said that several times. And he did not like it.'"
Rolling Stone also reported this revelation in July - a family friend of the Tsarnaevs told the magazine that Tamerlan's mother said he felt like there was "two people living inside him," and that his mother was convinced Islam would cure his "demons."
Tamerlan and his younger brother Dzhokhar are accused of bombing the Boston Marathon in April, killing three people and wounding more than 200 others.