I saw dark spot on his light colored shorts and it smelled like semen and it was slippery. My son was sleeping and when he woke up I saw it. Is this what you mean as ejaculation? Or is this different from ejaculation because he did not have sexual thought or action before it?

Ejaculation by wet dream. The kids are normally shy in front of their parents, so if you want me or someone else trustworthy to talk to him, the please let me know.
What you observed may be wet dream seamen ejaculation, and most of the middle eastern ethnic male they become baligh between 12 and 13.