In what was probably the first such attack on American soil, two gunmen opened fire outside the venue of a controversial cartoon contest on Prophet Mohammed in Texas on Sunday, only to be killed themselves as police returned fire.
None of the approximately 200 people attending the event billed as the "Muhammad Art Exhibit and Cartoon Contest" in Garland, northeast of Dallas, were hurt in the attack for which Islamic State militants are reported to have claimed responsibility.
Citing a federal law enforcement source, one of the suspects was identified by CNN as Elton Simpson, a resident of Phoenix, Arizona, who was convicted in 2011 of a terror-related charge.
Simpson is believed to have sent a tweet before the attack that read, in part, "May Allah accept us as mujahideen," the source cited by CNN said. It bore the hashtag #texasattack.
FBI agents raided Simpson's home in Phoenix on Monday morning. They are working to collect evidence, CNN said citing FBI.
FBI and local officials in Garland were also checking the gunmen's vehicle for explosives, and the area around the venue was blocked off.
The attack bears similarities to attacks this year on events in France and Denmark featuring images of Prophet Mohammed, which Muslims believe are blasphemous.
The keynote speaker at the event, organised by the American Freedom Defence Initiative (AFDI), was right-wing Dutch politician Geert Wilders, who was placed on an Al Qaeda hit list, CNN said.
According to police, two men drove up to the Curtis Culwell Centre in Garland, got out of their car and began shooting just as the contest inside was ending around 7 p.m.
An unarmed security guard, Bruce Joiner, was shot in the ankle. He was later treated at a hospital and released, police said.
Garland police, who were helping with security, fired back, killing both gunmen. The exchange lasted about 15 seconds, police said.
"The first suspect was shot immediately," Garland Mayor Douglas Athas told CNN. "The second suspect was wounded and reached for his backpack. He was shot again."
"We have no other indication that anyone else was involved," Athas said.
Sunday night's event invited cartoonists to send in caricatures of Prophet Mohammed. The group said it received more than 350 submissions. The winning entry was to get $10,000.
"The Islamic jihadis are determined to suppress our freedom of speech violently," AFDI president Pamela Geller told CNN. "They struck in Paris and Copenhagen recently, and now in Texas."
In January, 12 people were murdered by two Islamist gunmen at the French satirical magazine Charlie Hebdo, which had published cartoons on the Prophet.
The following month, a gathering of free speech activists in the Danish capital Copenhagen was targeted by a gunman, killing a film director.
In 2006, Danish newspaper Jyllands-Posten had published cartoons satirising Prophet Mohammed, triggering riots around the world in which at least 200 people are believed to have died, as well as attacks on several Western embassies.