GARLAND, Texas — Two gunmen were killed Sunday in Texas after opening fire on a security officer outside a provocative contest for cartoon depictions of Prophet Muhammad, and a bomb squad was called in to search their vehicle as a precaution, authorities said.

The men drove up to the Curtis Culwell Center in the Dallas suburb of Garland as the event was scheduled to end and began shooting at the security officer, the City of Garland said in a statement. Garland police officers returned fire, killing the men.

Garland police spokesman Joe Harn said it was not immediately clear whether the shooting was connected to the event inside, a contest hosted by the New York-based American Freedom Defense Initiative that would award $10,000 for the best cartoon depicting the Prophet Muhammad.

But he said at a late Sunday news conference that authorities were searching the gunmen’s vehicle for explosives, saying, “Because of the situation of what was going on today and the history of what we’ve been told has happened at other events like this, we are considering their car (is) possibly containing a bomb.”

Drawings such at the ones featured at the Texas event are deemed insulting to many followers of Islam and have sparked violence around the world. According to mainstream Islamic tradition, any physical depiction of the Prophet Muhammad — even a respectful one — is considered blasphemous.

The Curtis Culwell Center, a school-district owned public events space where the Texas event was held, was evacuated after the shooting, as were some surrounding businesses. The evacuation was lifted several hours later and police were not aware of any ongoing threat, but a large area around the center remained blocked off late into the night.

Harn said the gunmen had not yet been identified

The wounded security officer, who was unarmed, worked for the Garland Independent School District, Harn said. He was treated and released from a hospital.