In this link
http://www.nbcwashington.com/news/l...k-Slayings-Were-Held-Overnight-304161751.html
NG is interviewed, and on video says:
So when he knocked at the door, the front door, he told me that he could kinda sense, like somebody was extending, in front of the door, the inside, so he tried to knock more, and he went around, back, an the kitchen, you know the garage, sorry, when he went around, Savvas call him, and told him, oh I forgot to call you last night, but there it's ok....
It isn't made clear if he calls him on the phone or just calls him, as in calls out to him. I personally feel VF's husband saw him or at the very least actually spoke to him in person, whether from behind a door, through a window or face to face. This is just my opinion as NG doesn't clarify.