ISIS is taking responsibility for the shooting outside of a Texas community center that left the two gunman dead this past weekend. 

On Sunday, Elton Simpson and Nadir Soofi of Phoenix, Ariz. opened fire with assault rifles outside of an exhibit displaying images of the Prophet Muhammad in Garland, Texas. A security guard was injured, but authorities were able to shoot and kill Simpson and Soofi. No one else was injured.

According to NBC News, ISIS claimed ownership of the incident today: 

Charlie Winter, an NBC News counter-terrorism consultant, confirmed that ISIS said in an official radio broadcast Tuesday that two of its "soldiers" had carried out the attack in Garland, Texas.

Winter — who is also a researcher at the London-based Quilliam Foundation think tank — said the broadbast also warned that "worse" things are coming for America.

Although Simpson had been on the FBI's radar since the end of the last decade. While NBC notes that the ties to ISIS, Simpson and Soofi are unconfirmed, the New York Times reports that social media accounts likely linked to Simpson had reached out to proponents of ISIS: 

About the time of the attack Sunday, on a Twitter account with the name “Shariah is Light” that has since been suspended, someone posted using the hashtag #texasattack. The profile picture on the account is of Anwar al-Awlaki, a militant imam killed in a 2011 American drone strike in Yemen.

Mr. Awlaki repeatedly called for violence against cartoonists who, in his view, insulted the Prophet Muhammad. The Twitter post says that the writer and the man with him have “given bay’ah,” or pledged loyalty, “to Amirul Mu’mineen,” a title meaning commander of the faithful that was used by early Muslim rulers and has been claimed by Abu Bakr al-Baghdadi, leader of the Islamic State. “May Allah accept us as mujahedeen.”

The nonprofit Middle East Media Research Institute identified the account as belonging to one of the two gunmen, and said that some of his social media contacts were known supporters of the Islamic State.

Asked whether the Twitter account was Mr. Simpson’s, a senior law enforcement official briefed on the investigation said, “That’s certainly what we believe at this point.” The official, who spoke about the investigation on condition of anonymity, said there was no evidence so far that the attack had been directed or planned by a foreign terrorist group, though sorting out the communications between the attackers and militants using social media and other means would take some time.

[via NBC News and New York Times]