My step brother is really really starting to scare me and NO one will help what can I do?

I asked a question last week about my step brother and I got some great answers. I am going to ask another one because his behavior has become even weirder. My mom and I just moved from the states to New Zealand because my mom met a man she worked a few months with on a research project. The guy has a 17 year old son and is weird. He talks like a poet and will sit there and stare at you like he wants to kill you. Everyone in the area were I live has told me that he has very little friends because of his weirdness. The question I asked last week was about him standing over my bed when I woke up one morning and when I asked him why he said he was "contemplating" I called him weird and told him to get out of my room. I put a chair underneath the door knob so he could not come back in. He became even stranger (at least to me ) the next day. I came home from a friends house and I had flowers on my bed and a note that says for the "most beautiful woman in the world other than Mona Lisa". This freaked me out. I went and asked him what he was playing at and he said that "I will see". The worst part is I tell my mom this and she said that she will talk to my step-dad but I am over reacting and he is just trying to mess with me like any step brother would. She also believes that this is a ploy to cause issues because I am mad I had to move. Am i overreacting to this? Or am I right and this guy is not right in the head? I am only just 16 but this does not seem sane to me.