According to one report, a good friend had been killed, and the older brother became involved in religion shortly thereafter. I wonder what the circumstances of his friend’s death were?
The friend was murdered in September 2011 and he had “turned” long before that, so I doubt that had anything to do with it. Google Brendan Mess for the details.
People who knew the dead man and Tamerlan now believe Tamerlan was the killer.