GARLAND, Texas – Amid a call for a "Charlie Hebdo attack" in the United States, an officer who was part of the heavy security for a free-speech event called the "Muhammad Art Exhibit and Cartoon Contest" featuring Dutch politician Geert Wilders was shot outside the building shortly after the event concluded Sunday night.

Two attackers, who got out of their car on the street near the entrance to the parking lot and started shooting what witnesses described as an automatic weapon, were shot and killed by police. The injured officer, with the Garland Independent School District, was shot in the lower leg. Identified as Bruce Joiner, his injuries were not life threatening, and he was released from the hospital.

A SWAT team, which had been deployed on the site hours before the event, ushered attendees, including this reporter, into an arena in the building. An officer told WND two suspects were "down," but law-enforcement officers put a perimeter around them, fearing they may have had explosive devices in their car.

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Wilders left the building with members of his permanent Dutch security detail before the shooting.

Four hours after the incident, police helicopters continued to patrol as a Plano Police Department bomb squad worked on the scene, and a perimeter around the entire complex was still in place.

Surrounding businesses, including a Walmart and an Academy store, were evacuated.

One of the suspects was identified Monday morning as Elton Simpson, an Arizona man who had been previously investigated for terrorism, ABC News reported. FBI agents and a bomb squad were at his home in north Phoenix overnight.

A tweet from a jihadist who escaped while on bail for a cyber attack on U.S. military central command and fought for ISIS forces in Syria hailed the attack Sunday: "Allahu Akbar!!!!! 2 of our brothers opened fire at the Prophet Muhammad (s.a.w.) art exhibition in texas!"

On Thursday, a Twitter account purporting to belong to Mohamed Abdullahi Hassan, an American jihadist reportedly fighting in Somalia, called for attacks to be carried out in the United States similar to the massacre of the Charlie Hebdo cartoonists in Paris in January.

Hassan's tweet was accompanied by a link to a story about the event in Garland Sunday night: "The brothers from the Charlie hebdo attack did their part. It's time for brothers in the #US to do their part."

Prior to the event, a SWAT officer spoke to WND about the extraordinary security, which included a portable police tower, metal detectors at the entrance and a blockades outside.

"The reason why we have the security here is the reason why they would have it in France," he said. "What would make you think it wouldn't happen here?"

Geert Wilders' documentary "Islam Rising: Geert Wilders' Warning to the West" is available at WND's Superstore

The event was hosted by the American Freedom Defense Initiative, led by author and Atlas Shrugs blogger Pamela Geller, and author and Jihad Watch Director Robert Spencer, who both were immediately whisked away, separate from the attendees and media, after the shots were fired.

WND reached Spencer later Sunday night for his reaction.

"This attack shows how much our event was needed," he said. "The freedom of speech is under violent attack here in the U.S. now. We are at a crossroads as a nation now: Will we defend the freedom of speech or submit to violent intimidation?"

A local imam, Zia Sheikh, tweeted his dismay at the news.

"Shots fired at Pamela Geller event. The community stayed away from event. Seems like a lone wolf type of attack. Just what we didn't want."

Texas Gov. Gregg Abbott said in a statement Texas officials are "actively investigating to determine the cause and scope of the senseless attack in Garland, Texas."

"This is a crime that was quickly ended thanks to the swift action by Garland law enforcement," the governor said. "Our thoughts and prayers remain with all those affected tonight."

Later Sunday night, Wilders tweeted a photo showing him with members of the Garland SWAT team.

"Thank God the heroes of SWAT-team prevented the worst," he said.

The event attendees, who were put on lockdown in an arena at the center, which is owned by the Garland Independent School District, sang "God Bless America" and the national anthem as one attendee held up a U.S. flag. Two women then led in prayer for the injured officer, whose condition was unknown at the time.

See attendees pray for the injured officer (WND video):

In the arena, a witness of the shooting, John Roby of Oklahoma City, told WND he was heading out to his car when he heard what sounded like automatic-weapon fire coming from a black vehicle that had stopped on the street outside the center. Immediately, he heard two pistol shots, and a police officer screamed, "We've got the car, we've got the car."

See attendees singing the national anthem after the shooting Sunday night (WND video that Monday night was featured on the Fox News Channel's "The Kelly File" with Megyn Kelly):

Roby said the shooters were headed east on Naaman Forest Road outside the center, and the car was stopped in the road.

About 90 minutes after the incident, SWAT officers escorted media to their cars, which had been parked at a designated location. Attendees, however, were moved to another location away from the campus because police were still securing the main parking lot.

'Time for brothers to do their part'

The Curtis Culwell Center was the site of a Jan. 17 event one week after the Charlie Hebdo massacre, called "Stand With the Prophet in Honor and Respect."

Muslim leaders in the U.S, reacting to the worldwide solidarity with the satirical newspaper that published cartoons of Islam's founder, said they hoped the event would be the beginning of a "movement" to "defend Prophet Muhammad" and "defeat Islamophobia."

Two French-born Muslims carried out the Charlie Hebdo massacre, declaring their intent to "avenge the prophet." Eleven Charlie Hebdo staff members were killed.

The event Sunday featured a keynote by Wilders, who is regarded by the organizers of "Stand With the Prophet" as one of the world's worst fomenters of "Islamophobia."

Wilders told the Texas crowd he doesn't hate Muslims but believes Islam is an existential threat to Western civilization. He contends the "Islamization" of the West, primarily through immigration, should be aggressively opposed.

He commended the approximately 200 people in attendance for standing for free speech.

"Everybody present here tonight deserves respect just for being here," he said.

Wilders said it was no coincidence that at the same site in January, Islamic activists, shortly after the Charlie Hebdo massacre, "convened to demand that free speech be curtailed."

"They want to prohibit cartoons, books and films that they find insulting. And our answer is, 'Don't mess with Texas,'" Wilders said to cheers.

"Don't mess with the free West, and don't mess with our freedom of speech."

Wilders said the statement of everyone who attended is clear: "We will never allow barbarism. We will never allow Islam to rob us of our freedom of speech. Never."

As WND reported Thursday, three U.S. congressmen urged Secretary of State John Kerry and Secretary of Homeland Security Jeh Johnson to deny Wilders a visa ahead of his visit to the U.S., charging alleged ongoing "participation in inciting anti-Muslim aggression and violence."

He was in Washington at the invitation of Reps. Steve King, R-Iowa, and Louie Gohmert, R-Texas.

Wilders has been under constant security protection since November 2004, when two North African Muslims were accused of planning to murder him and another outspoken critic of Islam in the parliament, Ayaan Hirsi Ali. The Netherlands provides him with a security detail of up to six police officers, he wears a bulletproof vest, lives in a safe house and is escorted to work at the Dutch Parliament in an armored vehicle.

'Free society at stake'

Prior to the Garland event, artnet news editor Sarah Cascone wrote in a piece published by the Huffington Post that the Muhammad contest it "shameless Muslim-baiting.

But Spencer contends that few people seem to grasp that the very foundation of what makes for a free society is at stake.

WND asked him before the event if there was a way to accomplish his aims without being so provocative.

"No," he replied. "And the reason for that is because this has become the flashpoint for the defense of the freedom of speech. These cartoons are offensive to Islam, and there is a death penalty for those who blaspheme against Muhammad. The jihadis believe that these cartoons cross the line and those who draw them and publicize them have to be killed.

"If we believe in free speech in a free society, then we have to stand up for the right of people to offend Muslims or even subject Islam to mockery. If it were anything else, it would be the same," he said.

He noted that after the Charlie Hebdo massacre, the jihadists went to a kosher supermarket and killed Jews.

"What have the Jews done to provoke the Muslims?" he asked. "They were Jews."

"So, they're supposed to stop being Jews, what next? Well, I suppose pork and alcohol will then go. When does the Shariah compliance stop?"

"So, we're drawing a line now," he said, noting that in a free society people can have differing views and be offended without resorting to violence.

The risks that come with holding such and event are necessary, he said.

"This goes back to the founding principles of this nation, 'Give me liberty or give me death,' and, 'For these great principles we pledge our lives, our fortunes and our sacred honor.'

"If were not willing to stand for these truths and these principles that make for a free society, then we'll lose our free society," Spencer said. "And if we're not willing to stand even when the risks are as high as life and death, the death is what we're going to get, anyway."

Geller mobilized about 2,000 people to protest the "Stand With the Prophet" event in January.

She said the aim of her event Sunday was "precisely to show that we will not be cowed into silence by this violent intimidation."

"That is a crucial stand to take as Islamist assaults on the freedom of speech, our most fundamental freedom, are growing more insistent."

In 2010, she organized a group she estimates was 5,000-strong to march on the site of the proposed "Ground Zero Mosque" near the World Trade Center. The project eventually was canceled.

The ADFI art contest mirrored Danish newspaper Jyllands-Posten's publication in 2005 of editorial cartoons satirizing Muhammad, which prompted protests throughout the Middle East.

Charlie Hebdo cartoonist Renald Luzier, who designed the front page of the magazine that appeared after the Paris attacks, announced last week he will no longer draw Muhammad.

He insists "the terrorists didn't win," explaining that drawing Muhammad "no longer interests me."

A week after the Charlie Hebdo massacre, Australian artist Larry Pickering was put under police protection after threats arose in response to his depiction of Muhammad roasting on a spit as a pig.

In Belgium, a museum canceled an exhibition honoring the murdered Charlie Hebdo cartoonists, citing security concerns.

In February, Swedish artist Lars Vilks, who has faced numerous death threats for caricaturing Muhammad, was whisked away from a free-speech event in Copenhagen called "Art, blasphemy and freedom of expression" after shots were fired. Just hours later, a second shooting outside a Copenhagen synagogue left two dead and five police officers wounded.

Late Monday, the Fox News Channel's Megyn Kelly interviewed Spencer about the attack: