Context is important - I'm a writer.
I was out last night, pen and notebook with me enjoying an artisan cocktail in my favourite haunt and I was trying to solve a problem. I'm writing my second book and in the first one, there's a secondary but quite significant character. I realised that in my outline for book 2, she appears in one chapter, doesn't really do much then disappears and we never see her again.
That's a problem that needs solving so I scanned through the rest of my outline seeing if there was some other thread that she could be integrated into... and I found one.
Without boring you with the details, there's this young guy who's like a side character that pops up when his skill is helpful. He has a mission in book 2. He succeeds and escapes... Hooray. Nice kid. Difficult background, just needed a chance (that sort of thing).
So now the female will get involved and I'm sat there thinking 'How will this play out if she's there with him?'... And then I realise she'd help him, escape with him... and there's no way she won't, errrr... 'dispense' with him.
... Poor kid. I quite liked him.
The point is, he wasn't a character I planned on killing. It wasn't intentional nor was it done for shock value. It just came out of nowhere as I ran the situation through and watched it play out in my head... and I killed him. Well, she killed him - it was, after all, a progression of what my characters would do but I think that's what hit me, it felt like I didn't decide it - I had created a situation and it was inevitable. Maybe because of that, I actually feel bad about it, as if I watch dit unfold and couldn't stop it.
It was an interesting experience.
The good news is I think it's a good idea for the story and where it will take her character going into book 3.
But I suppose the real moral of the story is never be afraid to let your characters dictate their own actions. Just be careful... someone could get hurt.