Is He A Serial Killer? Or Is It Just Me..

Ok so lets just start of saying my mom met this guy on the internet. She chatted with him for a LONG time and finally they started to meet. One day i was coming out from getting my hair done and when i was about to enter the car.. My moms "internet friend" was in there. Oh and by the way this is from a few years back but ill start with the more present now. Anyways my mom and her internet friend built a very good relationship and he moved in. The mans good to her, he does whatever she asks, but hes quiet and weird.. Anyways its been about 3 years and i still feel the same way.. Even though we have talked and built a bond for eachother. He also has not changed meaning he is STILL quiet, sneaky, and weird. One time when my mom and grandmother were talking about him he went halfway up the stares and obviously was listening but my mom saw him. She didnt really take it seriously all she said was "ease dropping eh?" and laughed it off.. Anyways Ive always had a thought in my mind that he was a serial killer.. I mean hes quiet, hes sneaky, hes weird, and hes also not even from the state.. I started having dreams about him killing someone except me.. I dont know why but he never wants to kill me in my dreams and i think its because we bond REALLY good. Another weird thing though, is that when we talk about my mom.. Sometimes he gives hints of negativity for her like he sometimes stats her flaws, and just things to try and make me go against her and its weird but i let it go because everything he does, and says i record in my head.  Anyways one dream i had is when i had discovered he was a killer and i was threatening to tell mom but he held a knife behind his back and it looked like he was gonna stab my mother if i told.. since he was right behind her. Another dream i had was when he had me and my sister in the car. I knew I was in danger so i jumped out of the door.. Then i thought about my sister! But it was to late because when i got home she was nowhere to be found.. Then i heard pounding coming from the basement.. And she came out as a ghost and only i could see her :( she was saying "mommy! Mommy im here!" but my mom couldnt see her.. And thats when i burst out crying and i believe i woke up crying too. Anyways i cant remember the other dreams but finally i told my mom about them when me her and the man was in the car.. When i said i had dreams of him being a serial killer..  he seemed guilty, he had his hand on his forehead and his head was i dont know back on the seat.. He looked so guilty.. Anyways my mom said if you keep having these dreams, i may have to kill him myself and she was dead serious and after that confrontation.. i never had the dreams again.