Two gunmen have been killed and a security guard injured during what appears to be an attack on a contest for cartoon depictions of the prophet Muhammad in a Dallas suburb. The gunmen drove up to the Curtis Culwell Center in Garland shortly before 7pm on Sunday where the American Freedom Defense Initiative (AFDI) were hosting the exhibition and contest. According to city authorities an unarmed guard at the event was shot at before the men were engaged and killed by police. Authorities immediately locked down the center, evacuating the 200 participants at the event and sealing off large areas including a nearby shopping mall. A bomb squad was called in after reports of a possible incendiary device at the scene of the incident. Police said a "bomb container trailer" had also been deployed in which to place any suspect device.