An abundance of caution, or something more? The FBI continues to investigate the mass shooting by a Saudi pilot at the US naval base in Pensacola, but the Department of Defense now has to wonder about how well the rest of the trainees were vetted. For the moment, none of the Saudi pilots will have flight status, effectively grounding hundreds indefinitely — although classroom training will continue:

The Pentagon is suspending flight training and other operational exercises for Saudi military students studying in the United States while American officials investigate last week’s deadly shooting at Naval Air Station Pensacola by a Saudi airman, defense officials said.

The move is part of a “safety stand-down” ordered by Deputy Secretary of Defense David L. Norquist under which the military will review how it screens foreign military students and grants them access to bases.

Flight training and the other exercises are being halted for the roughly 850 Saudi trainees in the United States pending the completion of the review, which could take a week or more, officials said. That means Saudi pilots, including several hundred studying at Naval Air Station Pensacola and other bases in the state, will be grounded for the time being.

Classroom training will continue after being suspended over the weekend.

The move impacts more than 300 Saudi nationals in the US. Defense Secretary Mark Esper later said that the DoD wants to bring its vetting of foreign nationals in this program into parity with the vetting they do for American recruits, which makes sense — and should raise questions about why it took so long to think of that.

Still, even this pause prompts a few other questions now. The reasons for barring unvetted or poorly vetted personnel from powerful fighters and bombers is very obvious, but why is classroom training continuing? Shouldn’t the entire program be suspended while the DoD re-vets the visiting students? After all, the Saudi officer didn’t need a plane to murder three people and wound eight others at the naval base where military policy forbids the armed services from being, well, armed.

Second, just how well can the DoD vet these students anyway? How does the DoD plan to suss out radical Islamists from the application process when one’s own family allegedly can’t do it? The New York Times talked with family and friends of the shooter, who claim they never saw any hint of radicalization or mental illness in him:

“He never had a secret. He was never hiding anything,” Saeed Abdullah Alshamrani, 55, the lieutenant’s father, said at the family’s home in eastern Saudi Arabia on Tuesday evening. “It’s such a mystery. Even we don’t know the truth.”

“Are you sure he’s dead?” his father asked during the interview, surrounded by several relatives, acquaintances and others whose relationship to the family was not clear. “We haven’t even been given any proof of whether he’s dead or alive.”

No motive for the shooting has been determined, although the F.B.I. is treating it as a presumed terrorist attack. The Pentagon announced on Tuesday that it was suspending operational training for all of the nearly 900 Saudi military students in the United States.

Among the few clues to emerge was a tweet from an account that may be connected to Lieutenant Alshamrani and that condemned United States foreign policy decisions in the Middle East, according to the SITE Intelligence Group, which monitors extremist activity online. There was also a complaint the lieutenant filed this year against one of his instructors for mocking his mustache in class.

Another hint came a few months ago, according to a source in the investigation:

A person familiar with the investigation in the United States has said that friends and classmates told investigators that Lieutenant Alshamrani seemed to have become more religious when he returned from his last visit home in February.

During that visit, relatives said, he took his mother to the holy city of Mecca to perform the umrah, a type of pilgrimage that many Muslims routinely undertake. In his relatives’ eyes, however, they said there was nothing to indicate his Islamic beliefs had changed or hardened. He did not seem different, they said, except that he had shaven his chin clean.

Clearly something was different. And whatever that something was, the DoD missed it, either at the beginning of his training or later on. The suspension of training for the rest of the Saudi students seems a prudent move, as does the heightening of vetting standards, even if a belated consideration. If we are to take the killer’s family and friends at their word, however, one has to wonder whether it’s worth continuing this program at all if it means never having any clue as to when a foreign exchange military student might take advantage of his position to commit mass murder … for any reason.

At the very least, the DoD should consider allowing their personnel the means to defend themselves in case it happens again in the future. We call them the armed services for a reason.