GARLAND, Texas (AP) — Two gunmen were killed Sunday after opening fire on a security officer outside a provocative contest for cartoon depictions of Prophet Muhammad in Texas 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 contest was scheduled to end and began shooting at a security officer, the City of Garland said in a statement. Garland police officers returned fire, killing the men.

"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," Officer Joe Harn, a spokesman for the Garland Police Department, said at a news conference.

Police are not aware of any ongoing threat and had not received any credible threats before the event, Harn said.

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.

Such drawings 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 security officer who was shot worked for the Garland Independent School District, Harn said. He was treated at a local hospital for injuries and had been released Sunday night.

"Texas officials are actively investigating to determine the cause and scope of the senseless attack," Texas Gov. Greg Abbott said in a statement issued late Sunday.

The event featured speeches by Pamela Geller, president of the AFDI, and Geert Wilders, a Dutch lawmaker known for his outspoken criticism of Islam. Wilders received several standing ovations as he quoted former President Ronald Reagan and Texas founding father Sam Houston.

"Muhammad fought and terrorized people with the swords. Today, here in Garland, we fight Muhammad and his followers with the pen. And the pen, the drawings, will prove mightier than the sword," Wilders said during his speech.

Geller said during the event that her group had spent thousands of dollars on private security guards, several of whom could be seen standing on stage.