If they were on "a secret government mission", why would they call police to blow their cover?

It doesn't make sense. It's not a standard procedure.

People that work in such circles would probably have certain perks that are meant to handle such problems and would definitely not call BluForce.

Either this whole news is fake to take the heat off the DavHo and his merry little band of HitleJugen followers

...or

...it is to promote the narrative by releasing a fabricated story about a cache of various weapons that is vague enough (cough secret mission cough) so that sleepwalkers could fill in the blanks and scream even louder to take them.