Depending on the nature of the worksite, that's a pretty risky move by the intruder! My workplace is mostly occupied by menopausal women with sharp objects.

I was waiting to see a new psychologist at a place in sunshine once, and all of a sudden this dude came in, yelled at the receptionist, then started throwing things. It was kind of morbidly hilarious, because they had some sort of roller shutter system on the reception window (which was already that Perspex crap with the little paper tray gap thing) that they deployed as soon as he started trying to break things, all the keycard door things started flashing red, alarms started going off, and all the staff ran away from the reception. Meanwhile I was just sitting there with bins and bags flying past my head "um, hello? Anyone?"

Not knocking the reception staff, but in hindsight it makes me laugh how they all ran away so quickly. It was almost comical how quickly it all happened. I didn't get to see the aftermath, because after about a minute of old mate throwing things around, the psychologist I was seeing came out and took me to the psych rooms as if it was business as usual. Frequent flyer, I'm guessing