Two men who opened fire outside a contest for Prophet Mohammad 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.

An unamed 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."