The former lawyer for Elton Simpson, one of two gunmen who were killed Sunday after opening fire outside a Prophet Muhammad cartoon contest in Garland, Texas, says an FBI investigation that led to a 2011 conviction for Simpson probably made him "a better criminal."

“He learned that they were following him,” Kristina Sitton, who represented Simpson in the previous case, told the New York Times. “He learned how not to attract suspicion. He learned how to be a better criminal.”

The FBI taped hundreds of conversations between Simpson and a paid informant between 2006 and 2009. In 2011, Simpson was convicted of lying to federal agents about a planned trip to Somalia "for the purpose of engaging in violent jihad,” authorities alleged. But a judge sentenced him to three years' probation, saying the government failed to adequately prove its case.

Police say Simpson, 30, and his roommate, 34-year-old Nadir Soofi, traveled from Phoenix to Garland, where they opened fire outside the heavily guarded event Sunday night, wounding a security guard. They were both shot to death by a traffic officer.

"He never struck me as someone who would do this sort of thing," Sitton told ABC News earlier this week. "I'm not a bleeding heart, I'm a Republican. I've seen some pretty bad guys and he seemed pretty normal."

Sitton even described Simpson as "harmless."

"Converting to Islam seemed like a good thing for him," she said. "He had been going down a bad path and then he found Islam."

Sitton told the Times that despite going “on and on about dying on the battlefield" in the taped conversations, Simpson did not seem like a real terror threat.

“If you’d have asked me, I would have said he was just a talker," Sitton said.

According to the paper, the FBI's investigation of Simpson was "revived some months ago when he began expressing support for the Islamic State extremist group."

But it seems authorities, too, felt Simpson was just a talker.

"We'd been tracking his online activities," a senior law enforcement official told ABC News. "He's been on our radar for a long time — but there was no indication of any attack coming."

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