Not saying he would be a person who watched the news, maybe, but if this area is his stomping grounds, so to speak, surely he has seen the activity, the police presence, etc. and learned what was going on. It would be almost impossible not to.
Also, if he was known to Jill in any way, wouldn't her husband also probably be able to say he had seen him around and/or knew him too?
I got the impression he was a stranger to her, but not necessarily that he was accosting her on the video clip. It almost looked to me like she may have called him back to ask him a question. In any event they certainly had some sort of interaction and then it appeared that he walked away first.
I wonder if the man who said he did not see Jill walk past the place he stopped to eat saw this guy go by.