inital ideas

My initial plans are to either;
1. To have a boyfriend and girlfriend by a pond with the mood of being romance. There could then be a stalker follow then and then the stalker chase after them with a big knife. The stalker could then chase them into the wood and then the girl trips over a log and the stalker stabs her. The motive would be that the stalker would be jealous of the girl.
Or
2. A girl could be out shopping and a stalker follows her and takes pictures. Then you see the stalker in a black room developing the pictures. The stalker then adds the pictures to his wall of all the pictures of the girl and one stands out of the girl and her boyfriend. The stalker then goes into a big room with a chair and table with strange tools like a knife, pliers and a saw. The stalker then comes back to room with pictures and draws a line through picture of girl with the boy. The stalker then cleans the knife that was in the room on the table. The motive for killing the boyfriend would be obsession of the girl