A law enforcement source tells CBS News investigators now believe suspected Boston bomber Tamerlan Tsarnaev was "well on the road to radicalization " prior to his trip to Russia in 2012.
The source says an analysis of Tamerlan's electronic communications including emails, on-line chats and various video messages indicate that his radicalization had been underway before his 2012 visit.
Investigators continue to conduct digital forensics on the older brother's online discussions, including analysis of his demeanor and language in those interactions and his email exchanges.
They believe that much of his radicalization was inspired by AQAP--Al Qaeda in the Arabian Peninsula--including the on-line "Inspire" magazine and sermons by American-born cleric Anwar al Awalaki, who is also believed to have inspired the Christmas Day underwear bomber and others.
The source adds the visit to Russia remains a key component in the investigation.