National Security Adviser Robert O'Brien said Sunday the fatal shootings at a Pensacola, Fla., naval base by a member of the Saudi Air Force “appears to be a terrorist attack."

In an interview on CBS News’ “Face The Nation,” O’Brien cautioned that he did not want to “prejudge the investigation.”

"To me, it appears so be a terrorist attack," O'Brien said. "I don't want to prejudge the investigation, but it appears that this may be someone that was radicalized, whether it was here or it's unclear if he's got any other ties to other organizations."

The FBI identified Mohammed Saeed Alshamrani, 21, as the gunman who opened fire in a classroom at Naval Air Station Pensacola on Friday, killing three sailors and wounding two sheriff's deputies.

Alshamrani was killed after exchanging gunfire with the sheriff's deputies.

“This looks like something that's terrorism, or akin to terrorism,” he said.

"This is a guy who may very well have had said some things on Twitter that suggest he was radicalized," he said. "He went out and killed a number of Americans, so my point is it looks like terrorism."

O’Brien also weighed in on North Korea’s latest nuclear launch after he was asked if it was preparing for new nuclear tests.

“I hope not, that would be a mistake on the part of North Korea,” he said of nuclear testing.

“We expect [North Korean leader Kim Jong Un] to live up to the promise he made at the summit in Singapore” to denuclearize North Korea,” O’Brien said.