unknown slasher film?

I've been looking for this movie since I was 8 years old and I still can't find ANYTHING... I only remember one specific clip; it's a victim (a man) being taken to a dark, basement-style room where the killer (I only remember that he was dressed in black, maybe a leather mask? Like the collector), the killer decapitated him and impaled his head on a stake. Then, using the victim's phone (an old phone but with a touchscreen), he took a picture of the head and sent it to the protagonist. He attached the photo with the text "I'm home" or "i'm at Home" something like that. The protagonist saw the photo and was just confused, maybe he thought it was fake? Or I don't know, but in the photo the head looked like this (D:) and only a bit of the stake was visible, so maybe he thought it was a joke...? I remember the protagonist was on a bus at that moment. The victim was a friend of the protagonist btw