There is this guy that I go to school with who is a jerk to me about 75% of the time but sometimes he is really nice to me and I just don't understand the way he acts. So today I was in the library sitting alone on the computer so he came over ans started to use the computer next to me. I found it weird because he acts like he hates me and then he decided to sit by me when there were at least 20 other open computers. So he started to joke around with me and we talked for like 10 minutes before I left. About ten minutes later I was stressing out and was walking down the hallway crying, he generally acts like he would be happy if I was crying, but when he saw that I was upset he left his group of friends and came over and hugged me and asked what was wrong. When I wouldn't tell him he told me that I was a bad liar and even though we don't always get along he knows me better than that so then he started joking around with me to make me feel better. I guess I just don't understand why he acts like a complete jerk and that he can't stand me but the second when I break down he is the first one to make sure everything is OK and show that he cares, what does this mean?