From CNN:

ISIS has claimed responsibility for the attack outside a Prophet Mohammed cartoon contest in Texas — and warned of more attacks to come. In a broadcast on its official radio channel Tuesday, the group said two Al Khilafa soldiers opened fire outside the event in Garland, a Dallas suburb. Al Khilafa is how ISIS refers to its soldiers. The gunmen, Elton Simpson and Nadir Soofi, wounded a security guard before police shot and killed them. The ISIS radio announcer also referred to Simpson and Soofi as the terror group’s “brothers.”