Dream of building, chased, golden, person

I had a dream that I was at a high school, it had maybe a very mild resemblance to my school. And the school down by the football field for some reason had a beach. And this seal kept jumping out of the water to scare us. I was saying in my dream, "It has to stay in the water it can't hurt us". And then it popped out of the water can and started chasing me and some other person (I forgot or don't know who they were). It chased us up a ramp that led to the main school area. It started attacking everybody. I and the person I was with split up somehow, and I was hiding with multiple other people in some little room connected to the library. Then, (I forgot why) I decided to leave the building and hide behind the library. There was like a little narrow area between the library and this fence. So I stayed there for a bit. Soon enough, I decided to go back to the library room and I found everyone in there dead. There were multiple bodies scattered around the rest of the school too. I don't know now when or how, but at some point, it was a dog, and not a seal anymore. Some kind of golden retriever-looking dog. It continued causing chaos until some one I forgot whether it was me or someone else had a bow and arrow pointed at the dog, and was about to kill it. This was in front of the library as well. Then I don't get why but everyone started agreeing that it shouldn't be killed. So it wasn't killed and was just being treated like normal after killing so many students. After that I don't remember much other than that we were at some outside assembly or all the remaining people were just sitting in rows outside on the grass.