The Muslim terrorist who killed at least 49 people in an Orlando nightclub early Sunday was an angry loner who beat his ex-wife, alienated co-workers and made at least two mysterious trips to Saudi Arabia, according to people who knew him and law enforcement authorities who are now piecing together his descent into radical Islam.
FBI Director James Comey on Monday said that three phone calls between Omar Mateen and a 911 operator while Mateen was holed up in a club bathroom with hostages may provide insight into his radicalization. During those calls, Comey said, Mateen "made clear his support for" ISIS and pledged loyalty to the terror group's leader.
However, Mateen also "claimed solidarity" with the Boston Marathon bombers -- who learned how to make their pressure cooker bomb from an Al Qaeda-affiliated magazine -- and a man who blew himself up in Syria during an operation for Al-Nusra Front, leading Comey to say it was "unclear which terror group he aspired to support."
Another potential avenue of investigation is a pair of trips Mateen, 29, took to Saudi Arabia in March 2011 and March 2012 for umrah, a non-mandatory visit to Mecca for Muslims. Saudi Arabia's Interior Ministry spokesman confirmed the trips to The Associated Press in a text message Monday. Umrah can be performed at any time of the year.
MORE: West Catholic Prep graduate killed, FOX 29 intern recovering, FBI says Mateen had strong indications of radicalization, WATCH: Obama says no signs Orlando shooter was part of larger plot, Insights from Foreign Policy Research Institute and Phila. Director LGBT affairs, Philadelphia vigil planned as security upped, Obama cancels rally with Clinton, Man arrested in California with guns and chemicals, Muslim leaders condemn attack, Horror for one mother via text, Agonizing wait for families, Loved ones remember victims, Gunman's background, World holds vigil for victims, Why "No coincidence that this happened in Orlando," Terror massacre adds fireworks to presidential campaign, Christie: Attack shows US at war against terror, Texas lieutenant governor's controversial tweet, ATF shows types of guns fired.
Click here for the full story, including what Fox News learned about the trips to Saudi Arabia.