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GARLAND, TX. — Two men who opened fire outside a contest for Prophet Mohammed cartoons in a Dallas suburb were shot dead by police Sunday night, authorities said.

The men drove up to the Culwell Event Center in North Garland, got out of their car and began shooting just as the “Muhammad Art Exhibit and Cartoon Contest” inside was coming to an end, Garland police spokesman Joe Harns said.

A security guard was shot in the leg. He was later treated and released from a hospital.

Police who were helping with security at the event fired back, killing both gunmen, Harns said.

Their identities weren’t immediately released.

FBI and local officials were checking on the gunmen’s vehicle for explosives, a law enforcement official told CNN. The area around the center was blocked off.

Surrounding businesses, including a Walmart, were evacuated, as were attendees from the Curtis Culwell Center.

CNN producer Chris Lett, who was covering the event, said there were about 40 people at the event when police announced there had been a shooting.

The event, sponsored by the American Freedom Defense Initiative, claimed to have received “over 350 submissions of Muhammad cartoons from all over the world.”

Depiction considered blasphemy

While details about the gunmen, including their religion or their motive, weren’t immediately known, depictions of Prophet Mohammed are considered blasphemous by many Muslims.

The prohibition against illustrating the Prophet Mohammed began as an attempt to ward off idol worship, which was widespread in Islam’s Arabian birthplace. But in recent years, it has taken a deadly toll.

In January, gunmen attacked the officers of Charlie Hebdo, a French satirical magazine that has a controversial history of depicting Mohammad, and killed 12 people.

Shortly after the shooting, a prominent Muslim leader in Dallas said tweeted that the incident was “just what we didn’t want.”

“The community stayed away from event,” wrote Imam Zia Sheikh. “Seems like a lone wolf type of attack. Just what we didn’t want.”

‘This is a war’

The keynote speaker at the Garland event was right-wing Dutch politician Geert Wilders who was placed on an al Qaeda hit list for his film “Fitna.”

The film, which Wilders released online in March 2008 to international outcry, features disturbing images of terrorist acts superimposed over verses from the Quran in an apparent attempt to paint Islam as a threat to Western society.

In 2011, Wilders was cleared on charges of inciting discrimination and hatred over a controversial film he made about Islam.

The group, the American Freedom Defense Initiative, is considered an anti-Muslim group by the Southern Poverty Law Center, which tracks hate groups.

Its president, Pamela Geller, is “the anti-Muslim movement’s most visible and flamboyant figurehead,” the SPLC says.

Geller took to her own website shortly after the incident, writing, “This is a war. This is war on free speech.”