I don't think Kjell was the man seen by Fouke 'stumbling along' with a shuffling gait down Jackson Street because Fouke described the White Male as "medium heavy build, barrel chested.' Well Kjell was quite lean and of slim to medium build. I mean I used to think that maybe Kjell, if he was out walking a dog or just standing on his driveway, may have been doing so waiting for the Zodiac. But even if Kjell was just standing on his drive, which seems suspicious at first and could be seen as him waiting for someone he's been expecting but it could aslo just as easily be that he's come out onto the front drive because, as we know, Pacific Heights is an upper-middle class neighbourhood with many wealthy and well off residents residing there and he's come out in response to hearing the police sirens and lights. Armond Pelissetti said himself
"We responded to a radio call that told us that a cab driver was being robbed and/or possibly assaulted at the corner of Cherry & Washington Street in Pacific Heights. We, fortunately, were very close and responded to that corner and were able to do so with red lights and siren at 09:55 at night and got there very quickly."
So Kjell may have been reacting to the commotion. Zodiac would certainly have heard Armond approaching I'm sure.
