why does snape kill dumbledore

The Dumbledore/Snape discussion was about precisely that distinction - Dumbledore's suggestion was that it was killing, yes, but it would only be murder if Snape believed that it was, leaving Dumbledore to a worse fate (specifically at the hands of either Fenrir Greyback or "dear Bellatrix, who likes to play with her food before she eats it"). kakashi kill rin episode