I’m not prepared...help.

I know there are a lot of mothers on here with infants/toddlers/etc. But I’m sure there should be some parents with older children.

Tonight I walked in to the bathroom while my 9 year old son was taking a bath and apparently....masturbating. It shocked me, but I tried to have as little reaction as possible. I went in for something specific and just got that and left the bathroom. I know I need to address this, I mean at least he was in the privacy of the bathroom.

I’m not interested in shaming him, obviously. I want to approach this inevitable talk with an open mind and support....but that being said, I’m not even sure how to appropriately do that. Any suggestions or experiences? Thanks!