FBI Director James Comey added that it's difficult to determine which terrorist group may have inspired the shooter

The shooter who killed five people at two military sites in Chattanooga, Tennessee, in July was motivated by a foreign terrorist organization, FBI Director James Comey told reporters in New York on Wednesday, according to multiple reports.

“We’ve investigated Chattanooga from the beginning and we’ve concluded the Chattanooga killer was inspired by a foreign terrorist organization’s propaganda,” Comey said, according to The Times Free Press of Chattanooga.

Get push notifications with news, features and more.

According to CNN, Comey added that it’s difficult to determine which terrorist group may have inspired the shooter, Mohammad Abdulazeez, 24, who killed four U.S. Marines and one sailor before he was fatally shot by police.

“It’s hard to entangle which particular source,” said Comey, who twice called the shooting a “terror attack,” according to Fox News. “There are lots of competing poisons out there.”

• Want to keep up with the latest crime coverage? Click here to get breaking crime news, ongoing trial coverage and details of intriguing unsolved cases in the True Crime Newsletter.

The attack took place five months ago to the day, and the FBI initially hesitated to declare the attack “terrorism.”

Classifying the attack as terrorism would make the victims, all military servicemen, eligible for Purple Hearts.

In a statement obtained by PEOPLE, U.S. Rep. Chuck Fleischmann, who has advocated for the servicemen who died to be awarded Purple Hearts, said, “It has been five months, to the day, since our community was struck by this horrendous attack and I am thankful the FBI has finally recognized it as terrorism. It is my sincere hope that with this designation the victims will finally be awarded the Purple Hearts they so justly deserve.”

UPDATE: Just hours after FBI Director James Comey characterized the shooting as terrorist-related, Navy Secretary Ray Mabus posthumously awarded Purple Heart medals to all five victims, who were all servicemen, according to an announcement by U.S. Rep. Chuck Fleischmann obtained by PEOPLE.