Authorities in a Dallas suburb say two armed men who opened fire on a security officer outside of a contest for cartoons depictions of the Prophet Muhammad have been killed.

The city of Garland said in a statement posted on its Facebook page Sunday night that two men drove up to the Curtis Culwell Center and began shooting at a security officer.

The statement says Garland Police Department officers engaged the gunmen, who were both shot and killed.

The statement doesn't say whether the shooting was related to the event.

The statement says the gunmen's vehicle may contain an "incendiary device." A bomb squad is on scene.

Nearby businesses were evacuated.

The American Freedom Defense Initiative was hosting a contest that would award $10,000 for the best cartoon depicting the Prophet Muhammad.