My daughter used to have this happen and also would see things that led her to believe it was her guardian angel or God.
annisia, this is VERY common. Just google "hearing my name called" and you will find responses from people who hear their names called out at night. Some think it's a dream state, some think it's a supernatural thing, it's all up to interpretation.
It's common. It's not the same as "hearing voices" that we associated with psychosis. In those cases, the voices are persistent, often saying very disturbing things or sometimes saying unrelated things but they make it difficult for the person hearing them to hear reality around them.
I think everyone at some point has heard their name called out and there was actually nothing.
Well, it's either a nightmare, which can seem quite real during that half awake - half asleep phase, or a mental issue. The nightmare he will get over, but if it is truly a mental issue he needs to be in some sort of care. If this is the first time, I would try observing his behavior and see if it happens again. If it continues, psychiatric counseling may be in order.