What do dreams about cemeteries and dead people mean?

Ok, so last night I has a dream that I was in school coming from my chemistry class on my way to the last class of the day but I couldnt remember where to go. I walked in circles around the school trying to find the class but I just couldn't remember. So I text my sister to tell me because in real life we do have the same class but she never answered. I gave up finding my class and went into the library. The library in my dream was in the school, but to get back from the library to your class, you had to drive there. WEIRD ! Anyway, (getting to the point) we weren't in a car,but there were 5 of us going back to the school and I looked over and saw a cemetery. The cemetery was covered with ancient egyptian stuff like gold and jewels. Then I saw this guy in a coffin who was dead but he was an egyptian prince I guess because the cemetery was only for royal egyptians. I could see his face so well and I was at a distance, it was like I zoomed into the cemetery. Then I look over and see the police, they were there because someone robbed the cemetery. My phone starts vibrating and it's my sister, she tells me that we had double period chemistry, which means I was supposed to stay in the class I came from. -___- Then I kind of woke myself up because it was creepy !