Yes, I am sure inasmuch as I have heard this vividly recalled by relatives who frequently visited Germany in the 1970s. But if my anecdotal account isn’t enough

Yes, I am sure inasmuch as I have heard this vividly recalled by relatives who frequently visited Germany in the 1970s. But if my anecdotal account isn’t enough, do a Google search or Google Books search for e.g. "frankfurt airport machine gun" and you will see this made an impression on other foreign visitors to Germany in years and decades past.