Gunmen in Texas shooting were Phoenix residents

Federal agents had Phoenix resident Elton Simpson in their sights for years before authorities say he showed up with an assault rifle at a cartoon contest held to mock the Prophet Mohammed in suburban Dallas on Sunday.

Court documents indicate that the FBI in Arizona targeted Simpson for a criminal investigation as early as 2006, when agents paid an undercover informant to befriend him and act like he wanted Simpson to teach him more about Islam.

Federal agents grew more concerned about Simpson's plans to travel to Africa, study at a religious school and join a jihad, according to court records. He was eventually arrested and charged with lying about his intentions.

He was convicted and sentenced to probation because a judge determined that agents could not prove a connection to terrorism.

Simpson and another Phoenix resident, Nadir Soofi, were identified as the two gunmen who were shot and killed Sunday night after they tried to approach the cartoon contest in Garland, Texas.

Early Tuesday, the Islamic State group claimed responsibility for the attack.

The Associated Press reported an audio statement on the Islamic State of Iraq and Syria's Al Bayan radio station said "two soldiers of the caliphate" carried out Sunday's attack in the Dallas suburb. The group did not provide details and it was unclear whether the group was opportunistically claiming the attack as its own.

Simpson and Soofi wounded a security officer before police opened fire and killed the two men, who shared a northwest Phoenix apartment.

Texas law-enforcement officials had been prepared for trouble at the contest because the organizers knew the topic could be highly offensive to many Muslims.

Garland police spokesman Joe Harn said the department had added extra officers and SWAT teams in case anyone tried to harm the attendees.

Simpson's family released a statement to the AP on Monday evening emphatically stating that they knew nothing of their son's plans and confirming their support for law enforcement.

"We send our prayers to everyone affected by this act of senseless violence, especially the security guard who was injured in the line of duty," the statement read. "Just like everyone in our beautiful country, we are struggling to understand how this could happen."

But federal agents had long suspected Simpson would take violent measures to defend his faith, according to court records.

The FBI investigation into Simpson began in Phoenix in 2006 because federal investigators said Simpson was associated with someone who agents believed was trying to set up a terrorist cell in Arizona, according to federal court documents.

Agents elicited the help of an informant who befriended Simpson and met with him three or four times per week, according to court records. Simpson's lawyer said agents paid the informant $130,000 to build the case against her client.

"He was a really normal guy, a normal kid. He was kind and respectful," attorney Kristina Sitton said of Simpson. "The only thing that would stand out was that he was a pretty devout Muslim."

In a 2007 conversation, Simpson told the informant that "Allah loves an individual who is 'out there fighting (non-Muslims)' and making the difficult sacrifices such as living in caves, sleeping on rocks rather than sleeping in comfortable beds and with his wife, children and nice cars," according to court documents.

Simpson also said, "If you get shot, or you get killed, it's (heaven) straight way," according to court records.

By 2009, Simpson was more strident in the recorded conversations, telling the informant that he was tired of living under non-Muslims and "that his money and taxes are going toward their weapons," according to court documents.

Federal agents interviewed Simpson in early 2010, and those conversations became the basis of the government's case against him.

Simpson was convicted in March 2011 of lying to the FBI about traveling to Somalia for the "purpose of engaging in violent jihad." Simpson was sentenced to three years of probation.

Simpson avoided a stiffer sentence because a federal judge found that the government could not support its assertion that those statements were related to terrorism, according to court records.

Usama Shami, president of the Islamic Community Center of Phoenix, said he first met Simpson about 10 years ago but said Simpson was not regularly attending services at the mosque near Interstate 17 and Northern Avenue.

Shami said Monday morning that he is glad no one else was killed or more severely injured in the Texas shootings and said there was nothing about teachings at the mosque that would have encouraged engaging in violent behavior.

"If you look at people who have been radicalized, they haven't been radicalized in the mosque," Shami said.

Sitton said Simpson had told her that he was on a government "no-fly" list, which is a record of people designated as suspected terrorists and prohibited from flying to or from the United States.

Sitton said her former client may have "just snapped" when he heard of the Texas event mocking Mohammed.

Federal agents on Monday continued searching an apartment in Phoenix as part of the investigation into Sunday night's shooting. Sitton said she believed Simpson had lived with Soofi at the apartment complex at 19th Avenue and Thunderbird Road.

Soofi's mother told the Dallas Morning News on Monday that he'd been born at Presbyterian Hospital and spent the first three years of his life in Garland. Sharon Soofi, who now lives in a small town southwest of Houston, said her ex-husband was a moderate Muslim who wanted his children raised in his faith. And though her son was observant, she said, she'd had no clue that he was thinking of turning to violence to defend his understanding of Islam.

Neighbors in the northwest Phoenix apartment complex, including Tim Rains, who lives across from their unit, said they never saw anything out of the ordinary from the two men.

Rains said he has trouble walking because he has a bad heart. One afternoon, about a year ago, he said one of the men helped him from his car to his apartment after noticing Rains gasping for air.

"He came right up and offered to help," Rains said.

Rains was part of a group of 20 to 30 people who were evacuated Sunday when FBI agents and police officers raided the apartment complex at about 11 p.m.

Republic reporters Kody Acevedo, Jerod MacDonald-Evoy, Judson Tomaiko and Megan Cassidy contributed to this article in addition to the Associated Press and the Dallas Morning News.