ask for photo IDs, ask for business cards, ask for any other documentation they might have and let them know you'll be happen to forward everything to the appropriate attorney.
do not answer ANY questions...
ask your own...
and, as always, witnesses, cameras, photos, and videos are always a GREAT idea...
also, it is worth noting that your private and business places and spaces should be well equipped with redundant CCTV, preferably with vault security of the media storing the recorded and monitored content.
of course, either way you might still be dragged off...never to be seen or heard from again...
such is life with the Nazi Gestapo
enjoy!