On Tuesday, the Islamic State claimed responsibility for a weekend attack in Garland, Texas. The gunmen, Nadir Soofi and Elton Simpson were shot dead when they tried to attack a Muhammad cartoon contest.
An ISIS radio announcer referred to Simpson and Soofi as "brothers", but offered no evidence that the two gunmen were affiliated with the radical Islamic terror group.
"We say to the defenders of the cross, the U.S., that future attacks are going to be harsher and worse. The Islamic State soldiers will inflict harm on you with the grace of God. The future is just around the corner," the ISIS announcer warned.
Former FBI agent Tim Clemente said Simpson and Soofi may have plotted the attack without any help from ISIS.
"They may not have had formal contact (with ISIS). They may have had email communication or read communications from ISIS, but I don't think they were directed by ISIS.
"I think it's the other way around -- they were kind of applying for membership into ISIS. And so they were doing this act, sent out the tweet in advance because if they know there's a possibility they're not going to make it out of this, then they can't give recognition to what they were trying to do after the fact," Clemente said to CNN.