It was a young lad, probably late teens, I think it might be Cindy's son Steven who lived with Ian until a few years ago when he went to live with his real dad Simon Wicks. I might be wrong, I think we find out next week.
I think Ian looked up at the young fella and said "John" before it went off. Who on earth John is I don't know! I can't see why his son Steven would want to stalk him, it wasn't Ian's idea for him to move away like he did, Ian really didn't want him to go. From what I remember Steven went off to visit someone and decided to stay for good (can't remember now whether it was America or South Africa)