my cousin suffered from seizures multiple times a day from 6 months on due to a neurological brain disease. i found that he would often scream or make loud noises as a baby right before or during the seizure. His eyes would also be open and rolled back a bit. Sounds like your baby is all good, but it may have been a seizure. it must be frightening for you, it’s hard seeing a child like this and not knowing what’s happening. I would suggest take him to the hospital just to make sure he’s okay. if this happens again, i suggest time the episodes in case it is a seizure. if they last longer than 3 minutes you need to get to immediate help as they are most likely grand mal seizures ( I am no professional this is just what i know from my late cousins medical care) .