I've had it happen to me once in one of the earlier versions of A19. Day one, sometime in the early or mid afternoon. I came across the new "clothing store". (I forget its excact name) so I went in to look for some good clothes and a duster. I woke up some sleepers and while I was taking care of them I was suddenly hit on the side of my head by a bunch of green goo. I turned and there was a cop. It surprised the crap out of me. I had to run outside and wait for him to come out. From a safe distance I peppered him with arrows until he blew. I was glad I was at the clothing store because my plant fiber pants had a big brown stain on the back and they kind of smelled bad too.
Over 2500 hours starting in A16 and that is the one and only time I've ever encountered a cop that early. No mods, all vanilla.