Extremism

Omar Mateen may not have understood the difference between ISIS, al-Qaeda and Hezbollah

FBI Director James B. Comey said that during his 911 calls, Mateen said he was a supporter of the Islamic State, the extremist Sunni group also known as ISIS that controls a significant expanse of territory in Syria and Iraq. Media outlets linked to the Islamic State later claimed Mateen as their own, describing him as "one of the soldiers of the caliphate in America."

Mateen also mentioned the 2013 Boston bombing during his calls. That attack, which left three dead and more than 260 injured, was carried out by the Tsarnaev brothers. While the brothers were not found to be directly linked to a foreign group, they were partly motivated by a magazine published by al-Qaeda's affiliate in Yemen. (According to the Guardian, Mateen's admiration for the Tsarnaev brothers went back further. In 2013, Mateen is believed to have told the FBI that he knew the two bombers, though investigators later concluded that this relationship had been fabricated.)