What's wrong with my brother?

My brother is 16. He's been mumbling alot and acting very strange. Tonight we were watching TV when he turned to my mother and said "its us its us its us its us." She said his name and he shook out of it. His eyes were glazed over at first. We asked him to tell us what just happened but he told us he was playing with our dog, when in fact he was eating a snack and watching tv when he said that. Once he came around, he said he felt queazy like someone had knocked the air out of him. This isn't the first incedent. Someone please tell me what's wrong with my brother!