An announcement broadcast from an ISIS-controlled radio station in Syria referred to the attackers as “brothers” and warned “future attacks are going to be harsher and worse.”
The statement also said, “the Islamic State soldiers will inflict harm on you with the grace of God. The future is just around the corner.”
The exact role ISIS played in planning the attacks is not clear, but a counterterrorism source told Fox News that ISIS “had knowledge of the attack beforehand and that the same fighters encouraged the shooters.”
According to Fox, an ISIS Twitter account claimed to have been in contact with one of the gunmen just before the attack. Fox also reported a British ISIS fighter in Syria sent out a message praising the attackers less than an hour after the attack.
The FBI already had an ongoing investigation into one of the attackers, Elton Simpson, due to suspicious activity on social media. Simpson began posting about ISIS on Facebook and Twitter several months ago.
Simpson was also convicted of lying to the FBI in 2011 about a planned trip to Somalia, claiming he hadn’t planned a trip when in fact he had. Although he was found guilty, he got off without jail time after a judge ruled the government failed to prove that he wanted to go “for the purpose of engaging in violent jihad.”
The FBI said it had no knowledge that Simpson was planning an attack in Texas.
Simpson and the second attacker, another American Muslim named Nadir Soofi, were armed with assault rifles and body armor when they opened fire on the Curtis Culwell Center in Garland, Texas on Sunday.
After shooting a school security guard, both attackers were killed by a police officer stationed at the scene. The school security guard is expected to survive.