Whats the meaning of my dream ?

Im in a part of the earth where everything has gone to waste buildings are smashed , street lights have fallen down and zombies are the main inhabitants of the earth. Im with my best friend and some stranger, I can't see his face but I distinctly remember there being 2 people next to me. We're in a large building, made up of mainly glass and I see a mob of people heading my way, and instead of helping them, I lock the door and let them get mowed down by the zombies, I was just too scared to let them in and the people around me felt the same way. Then the zombies spot us and we start running and my best friend trips and I don't even hesitate to keep running. We're climbing a ladder to the roof, and the zombies are chasing us down, and the stranger is above me and as soon as he gets to the top, he pushes me down into the crowd of zombies, and I get surrounded, they jump at me and the weird thing is, I saw the faces of the people I normally associate with being the zombies.