The Chattanooga shooting is being investigated by the joint terrorism task force as an act of terrorism, U.S. Attorney Killian said at a press conference held Friday.
While it may be premature to speculate the shooter's motive, the FBI is still investigating whether the shooter acted alone, FBI said Friday.
FBI also confirmed the shooter, Mohammad Youssuf Abdulazeez, had two "long guns" and one handgun and at least one of them were purchased legally.
"The suspected was not wearing body armor but he was wearing a load-bearing best to carry magazines of ammunition while moving on foot," Ed Reinhold with the FBI said. In addition, Reinhold confirmed Abdulazeez never left the fenced-in area of the military base where all four marines were killed.
At this time, officials have no indication that the shooter was inspired by or directed by "anyone other than himself" and while they will not confirm this was an ISIS-inspired motive, they will be exploring that option.
U.S. authorities are looking into a trip to the Middle East last year made by the gunman who killed four Marines in attacks on military centers in Chattanooga, Tennessee, NBC News reported.
Abdulazeez left the United States in April, returned in November and traveled through Jordan.