Story highlights

Chattanooga shootings were "motivated by foreign terrorist organization propaganda," FBI chief says

Comments mark first time U.S. official has explained why Chattanooga was thought to be terrorism

Mohammad Abdulazeez shot and killed four U.S. Marines and a sailor in July

New York CNN  — 

The fatal shootings at a Navy reserve facility in Chattanooga, Tennessee, in July were “motivated by foreign terrorist organization propaganda,” FBI Director James Comey told reporters Wednesday in New York.

Mohammad Abdulazeez opened fire on a military recruiting center, then drove seven miles away to a Navy reserve facility, where he shot and killed four U.S. Marines and a sailor.

“There is no doubt that the Chattanooga killer was inspired, motivated by foreign terrorist organization propaganda,” Comey said, adding it’s difficult to determine which terrorist group may have inspired Abdulazeez.

The FBI has been investigating the shootings as a terrorism case from the outset, Comey said.

His comments mark the first time a U.S. official has provided details outlining why the Chattanooga shootings are thought to be an act of terrorism. Earlier this month, President Barack Obama cited the Chattanooga shootings along with the recent San Bernardino, California, attacks as terrorist incidents but did not elaborate.

“However, the terrorist threat has evolved into a new phase,” Obama said. “As we’ve become better at preventing complex, multifaceted attacks like 9/11, terrorists turned to less-complicated acts of violence like the mass shootings that are all too common in our society. It is this type of attack that we saw at Fort Hood in 2009, in Chattanooga earlier this year and now in San Bernardino.”

CNN’s Eliott C. McLaughlin contributed to this report.