Two gunmen who opened fire outside of a "Draw Muhammad" contest organized in the town of Garland, Texas, on Sunday, were shot dead after shooting and injuring a security guard. Here's a look at what we know about the incident — from the event to the attackers.
Garland Police said Monday that the two attackers used assault rifles.
They drove up to an entrance that was blocked by a squad car, got out and started shooting, said Officer Joe Harn, a police spokesman.
The attackers hit a school security guard in the leg. Harn told The Associated Press that a police officer shot at the gunmen, which subdued them and then nearby SWAT officers started firing. Harn originally said that a single police officer shot and killed both attackers with his service weapon, but told the AP Monday night that police didn't know who fired the fatal shots.
Who was involved?
Federal law enforcement sources have identified the suspects as roommates Elton Simpson and Nadir Soofi.
Authorities are still trying to determine whether the suspects carried out the attack on their own or had ties to international terror groups.
Simpson was known to the FBI. He was convicted of lying to federal agents give years ago about his plans to allegedly join a terror group in Africa. The federal law enforcement sources said the suspects' apartment complex in Phoenix was being searched.
The name of the officer who first shot at the gunmen was not immediately released. "He did what he was trained to do," Harn said. "Under the fire that he was put under, he did a very good job. And probably saved lives."
After the attackers were taken down, authorities cleared a wider area, fearing there might be explosives. Authorities detonated some suspicious items in the attackers' car, but no bombs were found, Harn said.
The security guard was treated at a hospital and released, he said.
Who organized the event?
The inaugural Muhammad Art Exhibit and Contest offered a $10,000 prize for cartoons of the Islamic prophet — depictions that are considered blasphemous by many Muslims around the world. About 200 people attended.
The event was sponsored by the American Freedom Defense Initiative (AFDI) and attended by its president and co-founder, Pamela Geller — who is also president of Stop Islamization of America (SIOA). Both are listed as hate groups by the Southern Poverty Law Center.
Geller, a prominent campaigner against plans for a mosque near Ground Zero, is author of "The Post-American Presidency: The Obama Administration's War on America." In 2013 she was reportedly barred from entering Britain, where she was due to speak at a rally organized by the far-right group English Defense League.
Among the speakers present was outspoken anti-Muslim Dutch politician Geert Wilders, who later tweeted a picture of himself in front of what he called a "SWAT team" of armed police officers.
Why was it held at a school arena?
The Curtis Culwell Center was chosen because it had previously hosted an Islamic conference — Stand With the Prophet in Honor and Respect — in January. That event was held one week after gunmen in France attacked and killed 12 people at the Paris offices of Charlie Hebdo, a satirical magazine which had published cartoons depicting Muhammad. The AFDI picketed the January conference and moved to hold its own event.
Some had questioned whether the Garland Independent School District, which runs the venue, should allow the event to go ahead.
However, school board President Rick Lambert told the Dallas Morning News that the convention center was a public facility and the district could not discriminate based on viewpoints. The AFDI paid approximately $10,000 for additional security at Sunday's cartoon contest, the newspaper reported.
Who was behind the attack?
Texas Gov. Greg Abbott issued a statement late Sunday calling the shooting "senseless." He said Texas authorities were "actively investigating to determine the cause and scope" of the attack.
The FBI was also involved in the investigation, NBC Dallas-Fort Worth reported.
The identities and motive of the suspects was not immediately clear. Police were unable to immediately search the bodies because a bomb squad robot was checking the suspects' vehicle for possible explosives.
It was not immediately clear if the gunmen were specifically targeting the event. However, the publication of cartoons of Muhammad has triggered violence in the past. Danish newspaper Jyllands-Posten's publication of a series of Muhammad drawings in September 2005 led to the burning of the Danish flag and attacks on Danish embassies around the Middle East. Cartoonist Kurt Westergaard was attacked at his home in 2010 by a Somali Muslim carrying an ax and a knife.
Paris magazine Charlie Hebdo, which repeatedly published Muhammad cartoons, was attacked on Jan. 7 by armed gunmen who killed 12 people.
The Dallas-Fort Worth chapter of the Council on American-Islamic Relations said it was "very closely monitoring" the situation.
"We have been in contact with various members of law enforcement in an effort to collect accurate information and assist them in their efforts to take safety precautions in response to the shootings," it said in a statement, urging prayers and calm.
Dr. Bilal Rana, president of Ahmadiyya Muslim Youth Association, expressed "shock and horror" over the Garland shooting.
"While we wait for investigators to tell us more about the shooters, we wholly condemn any such acts of violence and find them completely unjustifiable," Rana said in a statement, according to NBC Dallas-Fort Worth. "Our faith calls us to engage in dialogue. So we condemn any use of violence."