U.S. federal authorities were investigating two men killed by police in Texas after the men shot a security guard outside a venue holding a contest for Prophet Mohammad cartoons.
Police officials said the shooters were roommates Elton Simpson and Nadir Soofi, of Arizona. Court documents show that Simpson had been under surveillance since 2006 and convicted in 2010 of lying to FBI agents over his desire to join violent jihad in Somalia.
FBI agents and police searched the two men's home in Phoenix, cordoning off the apartment complex and evacuating residents for several hours.
An investigator talks to police officers at the Autumn Ridge apartment complex which had been searched by investigators in Phoenix, Arizona, May 4, 2015.
Joe Harn, a spokesman for the Garland, Texas, police department, said Monday that while the motivation for the attack remains unknown, "obviously they were there to shoot people." Police found ammunition and luggage in the attackers' car, but no bombs despite initial suspicions.
The guard was treated for a leg wound and released from the hospital.
Texas Governor Greg Abbott said state officials are investigating, and Dallas FBI spokeswoman Katherine Chaumont said that agency is providing investigative and bomb technician assistance.
President Barack Obama was briefed on the shooting Sunday night.
On Monday, White House spokesman Josh Earnest said, "We have seen extremists try to use expressions that they consider to be offensive as a way to justify violence, not just in this country but around the world. In the mind of the president, there is no form of expression that would justify an act of violence."
An organization called the American Freedom Defense Initiative, also known as Stop the Islamization of America, sponsored the Garland event, which included a contest for cartoons depicting Islam's Prophet Muhammad and offered a $10,000 prize for the winner.
AFDI executive director Pamela Geller said the event was "about freedom of speech."
The group's website said more than 350 cartoons were submitted to "show that Americans will not be cowed by violent Islamist intimidation."
The Southern Poverty Law Center, which maintains data on hate groups throughout the United States, calls AFDI an "anti-Muslim extremist" organization.
Oren Segal, director of the Anti-Defamation League (ADL) Center on Extremism, told VOA Monday, They're an extremist group because of the messages ... [Geller] puts out. I would say that she's so extreme at points, in terms of vilifying Muslims, that it creates an atmosphere that is not conducive to discussion.
"We've been concerned about Pamela Geller for several years," Segal added, "primarily because she is one of the leading American anti-Muslim bigots, consistently vilifying Muslims and the Islamic faith under the guise, of course, of fighting radical Islamists. They preach that Islam is inherently evil and she has said that she prefers that immigration from Muslim countries is limited."
Ahead of the event, Dallas Muslims had circulated messages on social media urging each other to ignore the event and not give the organizer any attention, Reuters reported.
Police in Garland told Reuters a bomb squad, the Federal Bureau of Investigation, a SWAT team and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives had been involved in preparations for security around the controversial exhibit and contest, for which organizers reportedly paid $10,000.
Geller posted photos on social media ahead of the event, posing with three heavily armed men wearing camouflage.
At the new conference, Harn also tried to distance the city from the meeting, which drew about 200 people, saying the group "really does not have much to do with Garland other than they rented the site."
AFDI's Geller described the shooting as a terrorist attack on her website, and said, “this is a war on free speech.”
She is known for her efforts to block the opening of an Islamic center near the site of the World Trade Center towers that were brought down in the terrorist attacks of September 11, 2001.
Dutch politician Geert Wilders, a critic of Islam who said last week the United States should ban Muslim immigrants, was the Sunday event's keynote speaker. He mentioned on Twitter the shots being fired and said he left the building after his address.
Reaction to caricatures
Many Muslims find depictions of the Prophet Muhammad to be insulting to Islam. The issue has sparked tensions with those who see the drawings as a free speech issue.
In January, two gunmen attacked the French satirical magazine Charlie Hebdo, which had featured multiple cartoons depicting Muhammad.
Last week, Charlie Hebdo cartoonist Renald Luzier said he would stop drawing Muhammad, saying the subject no longer interests him.
Matthew Hilburn contributed to this report. Some material for this report came from Reuters and AP.