GARLAND: Police and FBI on Monday searched the Arizona apartment of one of two gunmen shot dead on Sunday after they allegedly opened fire with assault rifles outside a Texas exhibit of caricatures of the Prophet Mohammad (PBUH).

Police in Garland, Texas, said they had planned security for months around the controversial exhibit and contest, and that a bomb squad, the Federal Bureau of Investigation, a SWAT team and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives were all in place on Sunday night in case of any incidents.

Police worked with the FBI to determine if the attack was a terrorist incident. No bombs were found in the attackers' car, police said.

“Obviously they were there to shoot people,” Garland, Texas police spokesman Joe Harn said at a news conference. “He did a good job,” referring to the police officer who shot the attackers dead with his duty pistol. The incident in the Dallas suburb was an echo of past attacks or threats in other Western countries against art depicting the Prophet Mohammad (PBUH).

In January, gunmen killed 12 people in the Paris offices of French satirical magazine Charlie Hebdo in what it said was revenge for its cartoons. Four others were also killed at a kosher market in the city.

Citing a senior Federal Bureau of Investigation official, ABC News identified one of the gunmen as Elton Simpson, an Arizona man who was the target of a terror investigation. FBI agents and a bomb squad were searching Simpson's Phoenix home, ABC said.

Phoenix's KPHO TV reported an unidentified second man lived in the same complex as Simpson, the Autumn Ridge Apartments. It was not immediately clear whether the two men lived in the same apartment.

The two-story apartment building was cordoned off, and residents were evacuated early on Monday, a neighbor told Reuters. Police and FBI vehicles were parked outside but officials declined to comment.

The event in Garland, Texas, organized by American Freedom Defense Initiative (AFDI), was called “Muhammad Art Exhibit and Contest” and offered a $10,000 prize for the best artwork or cartoon depicting the Prophet.

The event featured speakers including Geert Wilders, a polarizing Dutch politician and anti-Islamic campaigner who is on an al Qaeda hit list.

The AFDI, described by the Southern Poverty Law Center as a hate group, has among other activities sponsored anti-Islamic advertising campaigns in transit systems across the country.

Depictions of the Prophet Mohammad (PBUH) are considered offensive in Islam, and Western art that portrays the Prophet has angered Muslims and provoked threats and attacks from extremists.

ABC News said officials believed Simpson sent out tweets ahead of the attack, with the last one using the hashtag #texasattack. It said, “My bro and myself have given bay'ah to Amirul Mu'mineen. May Allah accept us as mujahideen. Make dua.”

“Bay'ah” means “oath of allegiance” in Arabic, and “Amirul Mu'mineen” is “commander of the faithful,” a title of caliphs and other Muslim rulers. “Dua” means “supplication.” The tweet was pulled from Twitter after the attack.

Security guard hurt

The attack on Sunday took place at about 7pm local time in a parking lot of the Curtis Culwell Center, an indoor arena in Garland, northeast of Dallas.

The two suspects drove up to the building as the event was ending, and opened fire with automatic rifles at an unarmed security officer, striking him in the leg.

Garland police officers who were assisting with security returned fire, killing both suspects.

Most of the 200 people attending the event were still inside the arena when the violence unfolded and unaware of what had happened until later.