Boys are naturally particularly curious about ejaculation. Offenders know this and will often show kids they abuse what ejaculation is.
It is perfectly normal to be curious. Some kids think they have not been abused because they went along with it. This is not true. Offenders use the fact that boys are curious to get them into a situation where they can assault them and make them believe it is the boy's fault.
It is NEVER your fault whatever you might have done.