Two men were shot dead by police after they opened fire outside an event centre hosting a controversial cartoon contest in the US state of Texas.
The bodies of the gunmen remained on the street outside the Culwell Centre in Garland, near Dallas, hours after they were shot dead last night.
Their identities had not been released so far.
A bomb squad was called in to search their vehicle as a precaution, authorities said.
The controversial event was wrapping up shortly before 7 PM when the two gunmen pulled up in a car and shot an unarmed Garland ISD security officer.
Seconds later, Garland police returned fire and killed the two gunmen before anyone else was hurt.
"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.
Police locked down the events facility to protect about 200 people inside. After people were evacuated, they were driven to a secure location to await questioning by the FBI.
"Texas officials are actively investigating to determine the cause and scope of the senseless attack," Governor Greg Abbott said in a statement.
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.
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 last night.
The event featured speeches by Pamela Geller, president of the AFDI, and Geert Wilders, a Dutch lawmaker known for his outspoken criticism of Islam.
The FBI is providing investigative assistance and bomb technician assistance, Dallas FBI spokeswoman Katherine Chaumont said.
