Investigators are working on the presumption that the shooting was an act of terrorism.

Rachel Rojas, the special agent in charge of the Federal Bureau of Investigation’s Jacksonville field office, said on Sunday that the presumption of terrorism allows law enforcement agencies to more quickly identify and eliminate any potential threats to the community. None have been identified so far, she said.

“Our main goal right now is to confirm whether he acted alone or was he a part of a larger network,” Ms. Rojas said at a news conference on Sunday. “We currently assess there was one gunman who perpetrated this attack, and no arrests have been made in this case.”

The 21-year-old gunman, Second Lt. Mohammed Saeed Alshamrani of the Royal Saudi Air Force, was fatally shot at the scene on Friday. A number of other Saudi students who were in the same training program are cooperating with the authorities, Ms. Rojas said. All international students in the program have been accounted for, she said, and the Saudi commanding officer has required his students to remain at Naval Air Station Pensacola.

“The Saudi government has pledged to fully cooperate with our investigation,” Ms. Rojas said.

Ms. Rojas declined to confirm many reported details about the gunman and the shooting, including whether a Twitter account that had posted a screed about “evil” America had been verified as his, when he had been radicalized, or when he lawfully purchased the handgun he used.