If your son is a young pre-teen or teen in most cases this is perfectly normal. Children this age have a ton of curiosity, and you definitely don’t want to squash that unless it's harming them and others in a significant way.

It’s perfectly natural for children this age to have curiosity about:
(and this goes for all genders)

• Sex
• Masturbation
• Sexual and gender identity
• Death and/or the macabre

Think back to your younger days. Even if you grew up in a culturally more conservative time did any of that stop you from having your own curiosities above any or even all of the above? Are you a serial murderer?

In most cases psychopaths are born with a damaged orbital prefrontal cortex, reinforced by environmental triggers but not always. This is a very, very small portion of society.

Obviously keep a reasonable eye on your son, but don’t squash his natural process of growth, that’s unfair.

If you’re worried about the “unknowns”, meaning what possibly is in his head, you could always invite your son to talk about it.

I will warn you however, if you show judgement and disapproval here you run the risk of breaking that trust and inhibition with him, and he’ll likely try to avoid these types of situations with you again for a period of his youth. Teens can be very sensitive to these things. It doesn’t take much for them to decide you’re a “foe” and not a friend. They don’t yet have your advantage of hindsight that would allow them to take in the world in a broader, more nuanced sense.