White House national security adviser Robert O’Brien said Sunday the fatal shooting at a U.S. Navy base in Pensacola, Fla., appears to be a terrorist attack.

O’Brien said on CBS' "Face the Nation" that it’s not yet known if the Saudi military officer said to have shot and killed three people on Friday was acting alone and said the FBI is investigating. ADVERTISEMENT

“I don't want to prejudge the investigation, but it appears that this may be someone that was radicalized, whether it was here or, you know, it's unclear if he's got any ties to any other organizations,” O’Brien added.

“What do you mean appears?” CBC’s Margaret Brennan asked. “Based on what?”

“I'm watching the same things that you're watching and the public reports. And this is a guy who may very well have said some things on Twitter that suggest he was radicalized. He went out and killed a number of Americans. So, my point is it looks like terrorism,” O’Brien responded.

He added that “we’ll have to wait to see what the FBI investigation shows” regarding motive, and said the Saudis have promised “full cooperation with the investigation.”

“We're going to take them at their word. And the FBI is very competent doing these things. They'll get to the bottom of it, and we'll have a full report. But my point is, it looks from what we're seeing in- in the public reports that this looks like something that’s terrorism or akin to terrorism,” O’Brien said.

The FBI identified Mohammed Alshamrani, a "2nd LT in the Royal Saudi Air Force who was a student naval flight officer of Naval Aviation Schools Command,” as the shooter on Saturday.

The Navy identified the three people killed in the shooting as Ensign Joshua Kaleb Watson 23, from Alabama; Airman Mohammed Sameh Haitham, 19, from Florida and Airman Apprentice Cameron Scott Walters 21, from Georgia, on Saturday. The three were students of the Naval Aviation Schools Command.

The shooter was also killed in the Friday attack.