It was the deadliest terror attack in the U.S since 9-11.
Omar Mateen traveled to Saudi Arabia twice for pilgrimages in 2011 and 2012. According to a friend, he became more and more religious.
The FBI interviewed him in two terror related cases, putting him under surveillance for 10 months, but both of those cases were closed.
Now FBI director James Comey said the agency is highly confident he was radicalized, mainly by viewing extremism on the internet and that he was inspired by foreign terrorist organizations.
John Sawyer is the senior researchers and special projects manager for START. He joined ABC2's In Focus to discuss what it means to be radicalized.
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