The Garland, Texas shooting is a new tactic for the so-called Islamic State—the first time it claims to have struck the U.S. at home.

GAZIANTEP, Turkey — The so-called Islamic State claimed responsibility today for the foiled attack on a controversial Prophet Muhammad cartoon contest near Dallas, Texas, that ended with both assailants being shot dead by a traffic cop. The announcement was made on the group’s radio station. But it remains unclear at this stage if the terror organization widely known as ISIS was involved in planning the attack and choosing the target or whether it merely inspired the assailants.

This would mark the first time ISIS has claimed it was behind an attack on U.S. soil. Until just a few months ago, U.S. officials were insisting the group was focused entirely on Syria and Iraq.

The Islamic State’s official radio station, al Bayan, first announced the claim for responsibility describing gunmen Elton Simpson and Nadir Soofi as “two soldiers of the caliphate.” In a news bulletin al Bayan said the event at the Curtis Culwell Center in Garland was targeted because it “was portraying negative pictures of the Prophet Muhammad.”

The report boasted of more attacks to come, warning,  “We tell America that what is coming will be even bigger and more bitter, and that you will see the soldiers of the Islamic State do terrible things.”

The apartment the assailants shared in Phoenix was searched Monday by FBI agents, who are trying to follow how the attackers plotted their operation and what their links might have been with foreign jihadists. Shortly before the attack Simpson tweeted he had sworn allegiance to ISIS.

As the Islamic State was taking credit for the attack, details were emerging of the background of Simpson suggesting his connections with overseas jihadists well pre-dated the Garland assault. Court documents show that Simpson had been under counter-terror surveillance since 2006 because he was associating with a man the FBI believed was planning to set up a terrorist cell in Arizona.

And in 2009 Simpson told a government informant that it was “time to go to Somalia,” adding, “We gonna make it to the battlefield.” His plan was first to go to South Africa and then on to Somalia.

In 2011 he was convicted for lying to FBI agents about his intentions of going to Somalia. A judge sentenced Simpson to three years’ probation and fined him $600 for lying to the FBI but ruled there was insufficient evidence to convict him on a charge of making a false statement involving international terrorism.

Both gunmen arrived Sunday at the Garland Center well prepared, wearing body armor and equipped with assault rifles. Their target was the crowd at a cartoon contest organized by the American Freedom Defense Initiative—a group dubbed anti-Muslim by many. The keynote speaker was the controversial right-wing Dutch politician Geert Wilders, who has long been on jihadists’ hit list.

Simpson and his companion were foiled by the quick wits of an off-duty traffic cop working after-hours as a security guard for the event. Armed only with his service handgun he killed both men, Garland Police Department spokesman Joe Harn told reporters Monday. “We think their strategy was to get into the event center, and they were not able to get past our perimeter that we had set up,” Harn said. SWAT team members are reported also to have fired at the suspects.

Federal and State officials were careful in the immediate hours after the attack to avoid describing it as a terror incident, saying they were still trying to establish the motives behind the armed men pulling up to a police perimeter and opening fire.

But much like the terror attack earlier this year in Paris on the French satirical magazine Charlie Hebdo that left 12 people dead it appears that at the very least jihadists overseas inspired the gunmen. Just before he and Soofi set off, Simpson tweeted “May Allah accept us as mujahideen.” He added that he and Soofi  had pledged loyalty to “Amirul Mu’mineen” (the leader of the faithful) — a reference to ISIS leader Abu Bakr al Baghdadi.

And after the shooting an online British ISIS fighter favored by Simpson celebrated in a tweet “Allahu Akbar!!!! 2 of our brothers just opened fire.” The fighter, who uses the nom de guerre Abu Hussein al Britani, has been identified by research groups that monitor jihadi websites as Junaid Hussain. He went on to tweet: “If there is no check on the freedom of your speech, then let your hearts be open to the freedom of our actions.”

The question now for U.S. counter terror officials is exactly what links the two men had with ISIS and whether the terror group actively orchestrated the attack.

In the Paris shootings in January, two brothers answering to Al Qaeda in the Arabian Peninsula carried out the attack on the satirical magazine. But an accomplice who killed a policewoman and four hostages in a kosher supermarket pledged his allegiance to ISIS. All three attackers were killed in shootouts with police.

A month later in Copenhagen a lone gunman attacked a conference attended by cartoonists who had drawn satirical images of Muhammad, then went after a synagogue. Two civilians were killed, several police wounded, and the shooter himself shot dead. — thedailybeast.com