It could be that the guards were armed but it was not obvious.
For example...
I once had a lunch where I ended up sitting at a table with three female detectives.
They were all wearing 'business suits' and one was teased/criticised for not 'wearing' her firearm.
(The others were assuming that she had it concealed in a bag.)
She laughed and moved her jacket, revealing the standard police automatic.
(In a 'shoulder holster' on her left hand side.)
She then started handing out business cards for the tailor, that had tailored the jacket to hide the firearm.
The other two were quite impressed with the result.
It was a bit of an experience for me.
The three women were young, intelligent, witty, well dressed, obviously healthy and physically fit.
I've never felt safer in my life.
(Even though they made the standard 'joke' that I'd heard many times before: "If the ◊◊◊◊ does down, we're hiding behind
you.")