Last Updated Dec 8, 2019 12:25 PM EST
National Security Adviser Robert O'Brien said that Friday's"appears to be a terrorist attack." The gunman was a member of the Saudi Air Force and an aviation student at the base.
"To me, it appears to be a terrorist attack," O'Brien said on "Face the Nation" on Sunday. "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 the shooter as Mohammed Saeed Alshamrani, 21. The gunman 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.
President Trump and top law enforcement officials have declined to say whether the shooting was terrorism related. A U.S. official told the Associated Press that Alshamrani and three others watched videos of mass shootings during a dinner party he hosted a dinner party earlier in the week.
O'Brien said the FBI doesn't know if Alshamrani was acting alone, but from what he is seeing in public reports, "this looks like something that's terrorism, or akin to terrorism." The Saudi government, he added, has committed to fully cooperating with the investigation.
"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."
A second lieutenant in the Royal Saudi Air Force, Alshamrani was a student naval flight officer of Naval Aviation Schools Command.
The Navy identified the three sailors killed in Friday's attack as Joshua Kaleb Watson, 23, Airman Mohammed Sameh Haitham, 19, and Airman Apprentice Cameron Scott Walters, 21.
O'Brien also discussed a test North Korea conducted at a rocket launch site, which it described as "very important."
When asked whether North Korea is preparing to restart nuclear tests, which Pyongyang suspended, O'Brien said doing so "would be a mistake on the part of North Korea."
"Kim Jong Un promised to denuclearize North Korea," O'Brien said. "We expect him to live up to the promise he made at the summit in Singapore, and we hope he'll do so."
O'Brien's comments follow a statement from North Korea's ambassador to the United Nations on Saturday that, though he noted that the comments contradict those publicly made by Kim.
The United States, he said is "continuing with our negotiations" and is hoping for a peaceful resolution.
"We have plenty of tools in the toolkit if North Korea takes a different path than the one it's promised its people, the people of South Korea, the United States, and the world," O'Brien said. "Kim Jong Un said he's going to denuclearize the Korean peninsula. If he does not do that, then we'll take that into account."
O'Brien alsoto "Face the Nation" host Margaret Brennan that Sergei Lavrov, Russia's foreign minister, could meet with President Trump in the Oval Office when he visits Washington this week. This is Lavrov's first visit to the U.S. since 2017, when he met with Mr. Trump at the White House.
The 2017 Oval Office meeting occurred one day after the president fired then-FBI Director James Comey. U.S. photojournalists were blocked from the meeting between Mr. Trump and Lavrov.