There’s some evidence he was radicalized before he got there:
Imam Suhaib Webb of the Islamic Society of Boston Cultural Center said on twitter that Governor Patricks office suddenly disinvited him to the service and he did not know why. The Clarion Project has documented the Muslim Brotherhood links of the ISBCC and its parent mosque, the Islamic Society of Boston.
Massachusetts Governor Deval Patrick and the Imam
City of Boston gave subsidy to bombing suspects radical mosque