Evil Things

Five college students leave New York City for a weekend in the country, and 48 hours later they vanished without a trace. To celebrate Miriam's (Elyssa Mersdorf) birthday, Aunt Gail (Gail Cadden) gives her use of a large country home in the Catskills for the weekend. Miriam invites her friends Cassy (Laurel Casillo), Mark (Morgan Hooper), Tanya (Torrey Weiss) and Leo (Ryan Maslyn) to join her to celebrate. Miriam, Cassy and Tanya bring the food and Mark brings the beer.As an aspiring filmmaker, Leo brings his new video camera, hoping to create a short documentary of the weekend getaway. The five begin driving to the house. Soon they are bothered by a black van. They suspect it to be following them and they find out this is true when the van rolls up another time through a diner. Mark, Cassy's boyfriend chases away the van angry at the driver for stalking them. They eventually make it to the house and Aunt Gail comes to turn the power on and wish them a good night. The five party and drink with Leo filming the whole occasion. The next day, they take a hike to the woods which they soon get lost in the dark and are scared by the sound of some sort of echo location being used by the "stalker". They do eventually make it back to the house. Later when eating dinner, they receive phone calls with no one answering.A knock at the door is heard and they receive a video tape. They watch it and it reveals that they are being secretly video taped since they were on the road. They have been filmed and stalked by the same person in the maroon van and much to their horror, he has also been inside the house and in their rooms while they were asleep. The power goes out and Mark tries to find the stalker because they hear the echo location sounds come from a room. He enters the room and finds a two way radio that is on.While looking at the others, the door shuts because one of the stalkers was behind the open door. He then presumably kills Mark. The door slightly opens and scared, they run upstairs and hide. They come downstairs with Tanya holding the camera and Leo leading the way. They get outside but Leo finds something outside and tells them to run back but Tanya falls breaking the camera and all left is the audio sound of Tanya screaming and her and Leo's fate is left unknown. The other stalker in the car watches Miriam run screaming into the woods. He gets out and most probably catches her with her fate unknown as well. The stalker with the camera now looks around the house for Cassy. After going into the living room, he sees her come out from behind the couch and because the house is dark, the stalker can see her with his nightvision on the camera but Cassy is wandering blindly. He follows her watching how far she will get. She gets to the door but sees something outside (implying there is more than one person involved with the stalker) and the camera man makes a the same echo location sound alerting her of his presence. He than lunges out at her leaving her fate unknown as well.The last piece of film shows the stalker with the camera in a park. While looking around he spots another group of friends filming. He then follows them on their trip.

Question: Who is Cassy's boyfriend?
Answer: Mark