Two law enforcement officials who asked not to be named identified one of the dead shooters as Elton Simpson, under surveillance since 2006 and convicted in 2010 of lying to FBI agents over his desire to join violent jihad in Somalia. The second shooter was identified as Nadir Soofi, a roommate of Simpson, according to two sources close to the investigation.
Phoenix FBI spokesman Perryn Collier confirmed agents were at the Autumn Ridge Apartments in connection with the shooting in Texas. The complex in north-central Phoenix was cordoned off and residents were evacuated for several hours in the early morning.
The shooting incident in the Dallas suburb of Garland was an echo of past attacks or threats in other Western countries against art depicting the Prophet Mohammad. 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.
The latest incident unfolded on Sunday, when a car drove up behind an indoor arena in Garland, where 200 people attended an event featuring caricatures of the Prophet Mohammad, portrayals considered offensive by Muslims.
Two men jumped out of the car and fired on security guards, injuring one. One police officer returned fire and killed both men in the parking lot.
Those inside the Curtis Culwell Center who had gone through heavy security to enter the event were not aware of the attack until afterward.
Police and federal agents had planned security for months ahead of the event organized by American Freedom Defense Initiative (AFDI), a free-speech organization that is also described as a hate group, and that paid $10,000 for extra protection.
The shooters wore protective gear and had extra ammunition in their car, Garland police spokesman Joe Harn said. No bomb was found in their vehicle.
"Obviously they were there to shoot people," Harn said at a news conference.
Referring to the police officer who used his duty pistol and killed the attackers, Harn said, "He did a good job."
At Autumn Ridge in Phoenix, policed searched both an apartment and a white van parked outside, with its side windows broken.
Bob Kieckhafer, 54, who lives one floor above and across from the apartment that was searched, said FBI and other law enforcement in SWAT gear evacuated people in the building at 11 p.m. late Sunday and did not let them back until 4 a.m.
He said two men lived in the apartment that was being searched by authorities. He described them as "just like your next-door-neighbor type of guys."
It was not immediately clear if both gunmen had lived in the complex, or if they shared an apartment.
Wanted to join jihad
Simpson, identified as one of the dead shooters, according to the two law enforcement sources, was convicted in 2010 of lying to FBI officials over discussions he had with an informant about his desire to travel to Somalia to engage in violent jihad.
According to court records, Simpson waived his right to a jury trial and was tried before then-U.S. District Judge Mary Murguia, who found him guilty of making a false statement and sentenced him to three years probation and ordered him to pay $600 in fines and penalties.
Murguia said there was insufficient evidence to conclude the false statement involved international terrorism.
The court documents say federal authorities began monitoring Simpson in 2006 because he was associated with an individual the FBI believed was trying to set up a terrorist cell in Arizona.
At one point, according to the documents, the FBI tried "unsuccessfully" to put Simpson on a U.S. government no-fly list.
ABC News said officials believed Simpson sent out tweets ahead of the attack, with the last one using the hashtag #texasattack.
Simpson's father told ABC News his son was "always a good kid" but said they had "some very serious differences."
"We are Americans and we believe in America," Dunston Simpson told ABC News. "What my son did reflects very badly on my family."
U.S. authorities were investigating possible links between the gunmen and international terrorist groups, a government source said.
A fighter for Islamic State, a militant group that has taken over large parts of Iraq and Syria, said in a tweet that "2 of our brothers just opened fire at the Prophet Muhammad (s.a.w.) art exhibition in Texas," according to the SITE Intelligence Group, a U.S.-based monitoring group. S.A.W. is an abbreviation for "May Allah honor him and grant him peace."
Free speech or hate
The AFDI event in Garland was called "Muhammad Art Exhibit and Contest" and offered a $10,000 prize for the best artwork or cartoon depicting the Prophet.
Depictions of the Prophet Mohammad are considered offensive in Islam, and Western art that portrays the Prophet has angered Muslims and provoked threats and attacks from extremists.
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.
(Additional reporting by Mark Hosenball in Washington, D.C., Nancy Wiechec in Phoenix, Arizona, Lisa Garza and Laura Buckman in Garland, Texas, Colleen Jenkins in Winston-Salem, North Carolina, and Julia Edwards aboard Air Force One; Writing by Fiona Ortiz and Ian Simpson; Editing by Frances Kerry and Jeffrey Benkoe)
