Really, I assume you can cite that rather extreme statement?
The veteran’s of our nations military and naval forces are a rather small minority overall. Just because many veterans have the skills, they don’t have the motivation to murder. Of course, there are exceptions.
Its the drugs, man, and their misdiagnose and misuse of which shooting massacres are only one effect. These drugs knock down the ordinary moral inhibitions that prevent such violence in the normally socialized citizen.
Maybe I could get a federal grant to do a formal study, but as you say yourself, “a rather small minority” which makes the percentage numbers even more surprisingly high for veterans and active duty. But I was a bit broader than that -”military connection” which boosts the numbers even higher since I did limit it to adult perps (I probably should have said “non-student perps” for greater accuracy.
You’ll probably have to look a lot harder for a long list of non-student, perps without a military connection that I would to put together a list of those with a military connection.