From the Washington Examiner :
Omar Mateen, 29, told his Facebook friends that he and other Islamic State affiliates were preparing multiple revenge attacks on the U.S.
“You kill innocent women and children by doing us airstrikes..now taste the Islamic state vengeance [sic],” Mateen wrote. “In the next few days you will see attacks from the Islamic State [ISIS] in the usa.”
Although investigators do not believe Mateen was a member of the Islamic State, he pledged loyalty to the group during multiple 911 calls he made before and during the attacks at the Pulse nightclub.