FBI said Sydney gunman prone to violence years before siege

A November 2009 memorandum from an FBI office in Australia to agency counterterrorism and international operations officials said that while Monis was not believed to be a threat to national security, "his ongoing offensive and nuisance behavior has the potential to incite others to violence."

A shotgun-wielding Monis took customers and workers captive in a December 2014 siege at the Lindt Cafe in Sydney and demanded to be delivered an Islamic State flag, an incident that fueled anxiety about the extremist group's expanding influence across the globe.

Though it's been established that Australian authorities failed to detect that Monis was a threat, despite years of warnings, the memo shows how the FBI was itself concerned about his rhetoric even before the Islamic State group emerged as a prominent international force and well ahead of the siege.

The memo noted that Monis, who also went by the name of Sheikh Haron, maintained on his website "inflammatory and fundamentalist material regarding the Islamic religion, jihad, suicide bombings and terrorism."

An Australian government review last year found no major faults with multiple agencies that failed to detect the threat Monis posed, despite his being out on bail on sexual assault and accessory to murder charges when he launched the attack.