Garland shooting: Prophet Mohamed cartoon contest organisers condemn attack as 'war on free speech' after police kill two gunmen

America is again confronting the spectre of domestic Islamic extremism after two gunmen, at least one of them a self-styled supporter of Isis, were shot and killed after attacking an exhibition of cartoons of the Prophet Mohamed.

Police searched the Autumn Ridge Apartments in Phoenix, Arizona, which is believed to be the home of the extremists who carried out the attack in Texas on Sunday night at an event hosted by a controversial group that claims to promote free speech. The incident echoed the assault on Charlie Hebdo magazine in Paris and other publications that have printed images of the Prophet.

The event in the town of Garland, near Dallas, was organised by the American Freedom Defence Initiative (AFDI) and titled the “Mohamed Art Exhibit and Contest”. The AFDI is headed by Pamela Geller, who has been linked to poster campaigns on buses that were denounced as anti-Muslim.

Ms Geller said the venue for Sunday’s competition was chosen because it was where American Muslim leaders held a conference on combating Islamophobia a week after the Paris attacks.

Response on its Facebook page to the shooting, the AFDI posted: “This is war on free speech. What are we going to do? Are we going to surrender to these monsters?”

One of the men was named by officials as Elton Simpson, of Phoenix, who was previously identified by the FBI as a jihadist terror suspect. The other gunman was named as Nadir Soofi.

Simpson was believed to have made threats on Twitter before the attack and voiced support for Isis. In 2011, he was convicted of lying to the FBI, which was investigating him over a trip he was planning to Somalia. A court heard that he had told an informer he wanted to wage holy war.

Ms Geller defended her decision to hold the art contest, which offered a $10,000 (£6,600) prize for the best artwork or cartoon depicting the Prophet, and which included the right-wing Dutch politician Geert Wilders among its speakers. “This shows the need for such conferences. The jihad is raging,” she told CNN. “We had on display various depictions of the Prophet Mohamed over the last 1,400 years. It was very well received. The winner was a former Muslim.”

Simpson and Soofi attacked the Curtis Culwell Centre arena in Garland at 6.50pm. They pulled up in a car, got out and opened fire with assault rifles, hitting an unarmed guard in the leg. Joe Harn, of Garland police, said the authorities had been arranging security for the event for months, aware of the potential for controversy.

The police were backed by a bomb-disposal team, FBI agents, an armed-response unit and the US Bureau of Alcohol, Tobacco, Firearms and Explosives, and the AFDI paid $10,000 of the costs. The two gunmen were killed by a traffic officer. “He was shooting with a pistol,” Mr Harn said. “He did a good job.”

Reports said that, before the attack, Simpson posted messages on a Twitter account that used an avatar image of the US-born Islamist cleric and al-Qaeda leader Anwar al-Awlaki, who was killed in a drone strike in Yemen in 2011. “The bro with me and myself have given bay’ah [an oath of allegiance] to Amirul Mu’mineen [commander of the faithful]. May Allah accept us as mujahedin. Make dua [supplication] #texasattack,” said the Twitter message.

Asked if the incident was terror-related, Mr Harn said: “We are looking at that... Obviously, they were there to shoot people. We know they were willing to pull [their guns] and start shooting at police.”

Additional reporting by agencies