While the FBI is presuming the fatal shooting of three at a Pensacola, Florida, naval base on Friday was terrorism, it has yet to declare an official motive.

In a news conference Sunday afternoon, Rachel L. Rojas, the FBI's special agent in charge in Jacksonville, said federal, state and local authorities are investigating the attack by the suspect, identified as Mohammed Saeed Alshamrani, 21, a second lieutenant in the Royal Saudi Air Force who was in a training program at Naval Air Station Pensacola. A sheriff's deputy killed him during the attack Friday morning.

The Navy identified the dead late Saturday as three aviation students: Ensign Joshua Kaleb Watson, 23, of Coffee, Alabama; Airman Mohammed Sameh Haitham, 19, of St. Petersburg, Florida; and Airman Apprentice Cameron Scott Walters, 21, of Richmond Hill, Georgia.

The main goal of the investigation is to find out whether Alshamrani acted alone or whether he was part of a “larger network,” but authorities stressed Sunday that the community is safe and they do not suspect any other immediate or direct threats.

“This is our chance to get this right and I'm going to take my time,” Rojas said about the investigation.

Authorities are also working to discern if an ideology was a motivating factor in the attack, and are “working with the presumption that this was an act of terrorism,” Rojas said.

Agencies will continue to conduct interviews to learn more about the shooter.

Alshamrani had invited three Saudi flight students to dinner in the past week and showed them videos of mass shootings, but investigators believe they had nothing to do with the attack. Rojas said Sunday that no arrests have been made in the case.

“There are a number of Saudi students who were close to the shooter and continue to cooperate in this investigation,” Rojas said. All international students on the Pensacola base are currently accounted for, and Rojas thanked Saudi Arabian officials for their cooperation in this investigation. She added the Saudi commanding officer has “restricted” other Saudi students to their base.

Although non-citizens are normally prohibited from buying handguns, Alshamrani had a valid hunting license, which allowed him to legally purchase his weapon from a dealer in Pensacola, law enforcement sources told NBC News on Saturday.

Lt. Col. Dave Eastburn, a Pentagon spokesman, said the suspect had been scheduled to complete a three-year U.S. Air Force Foreign Military Sales training program, funded by Saudi Arabia, in August.

Authorities believe a social media post critical of U.S. support for Israel and claiming America is anti-Islam belongs to Alshamrani. The post, which appeared before the shooting, is no longer live.

Law enforcement sources say investigators believe the shooter returned to Saudi Arabia after starting his U.S. training in 2017, and when he returned in February, he stopped socializing and going out as much with the three friends.

In addition to the three killed, eight people were injured in the attack, including two local sheriff's deputies who exchanged gunfire with the shooter.