PENSACOLA, Fla. - Training international students at Navy Air Station Pensacola is a core part of the base's mission.
The base was the site of a deadly shooting Friday when a Saudi national opened fire, killing three people and wounding several others.
The suspect was one of 852 Saudi nationals in the United States training under the Pentagon's security cooperation agreement with the Kingdom of Saudi Arabia, according to a Defense official.
The shooter, identified by three sources as Mohammed Alshamrani, began his three-year course August 2017 with English, basic aviation and initial pilot training, said the officials, who were not authorized to speak publicly due to the ongoing investigation.
Alshamrani had joined 5,180 foreign students from 153 countries in the United States for military training. Many of those students operate U.S. military hardware that foreign governments buy from the United States. Saudi Arabia is the world's largest customer for arms, and many of those are American made.
It's unclear what aircraft Alshamrani was training to fly, according to a second Defense source. However, the Saudis fly a variety of warplanes, including F-15 fighters and C-130 cargo aircraft.
Foreign military trainees are vetted before traveling to the United States. U.S. embassy personnel research data bases for activities such as support for terrorism, drug trafficking, corruption and other criminal behavior. Travel orders are denied to those who fail to pass the screening, the official said.
The base employs 16,000 military and 7,400 civilian personnel. This includes major tenant commands: Naval Aviation Schools Command, Naval Air Technical Training Center, Marine Aviation Training Support Group 21 and 23, the Blue Angels (the Navy's Flight Demonstration Squadron), and the headquarters for Naval Education Training Command, a command that combines direction and control of all Navy education and training.
International students can complete all or part of the typical 18-month syllabus on base and must go through several federal vetting processes before training at NAS Pensacola.
"The way that program works is that the foreign government has to certify that these are the best of their best, that these are their future generals and admirals and senior military officials for their countries," said U.S. Rep. Matt Gaetz, R-Fla. "The U.S. State Department does a scrub on those prospective trainees, and after that they matriculate into the program.
"That's a really important part of what our military does because it has people use our systems and train alongside our military members," he added. "They are more receptive and more capable and more willing to work with us when the time arises, should U.S. interests be impacted."
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Ozzie Nelson, a terrorism expert with the Center for Strategic and International Studies, said members of foreign military services who get selected to train at U.S. bases are top-notch candidates who undergo "extensive screening" not just by their own governments, but by the United States.
"The vetting of these individuals is so high, so thorough, this is not the group you'd expect it from," said Nelson, a former Navy helicopter pilot who served at the Pensacola base. "These programs are extremely successful, and they're of benefit to both the United States and the countries that send them over."
Nelson said Friday's shooting spree - on a secure base by someone who almost certainly underwent thorough background checks - reflects the pervasiveness and complexity of modern mass shootings.
Nelson described the purported Saudi assailant as an "outlier," and said he knows of no previous attacks by foreign military personnel inside a domestic military installation.
"It's not just schools. It's even our most secured facilities - like military bases - that are susceptible to these events," he added. "This is going to have implications…for the entire foreign national (training) program. We have to be very deliberate in how we analyze this."
Sean Clements, a media relations chief at Luke Air Force Base in Arizona, declined to discuss screening procedures for foreign pilot trainees because background checks are handled by headquarters.
However, he noted that military personnel from a half-dozen countries study and fly at the Glendale air field, learning to pilot F-35 and F-16 fighter jets.
Clements said Luke bans firearms possession by anyone on base other than military police, and performs screening and random searches of vehicles at the entry gate. However, he noted, hundreds of motorists pass through daily, and not all can be checked.
Clements said additional security measures are implemented when threat levels elevate, and base personnel go through regular training to address mass shootings. plane crashes and other catastrophes.
A recent report for the Department of Justice on "Policing Issues in Garrison Communities" listed several mass shooting events in the past decade, but none involved foreign military at U.S. bases.
The report said the Pentagon will, over the next few years, become responsible for all background checks for military contractors and civilian employees of the Defense Department.
This article originally appeared on USA TODAY: NAS Pensacola shooting: Why the base has international flight students