What constitutes a no-bounty stealth kill?

I would like to know how Skyrim determines whether I was detected killing someone. For example: There is this temple in Makreth, where there are some women down below the main hall. I lockpicked my way there, they stopped me and things ultimately led to a fight. I killed them, nobody was around to see it, yet when I came out of the temple, the guards were all over me...

I wasn't in stealth when fighting, because there were no witnesses whatsoever, so why was I still considered a killer?

I've found that if you attack some one and they survive the first hit, they some how telepathically tell the guards, at least in towns.

A "stealth kill" is really any situation where you one-hit kill someone and no-one sees.

This is normally done while sneaking as you will get the damage multipliers (i think its X2 for bows and X3 for melee without perks) which make it a lot easier to do.

It's 3x for bows, 6x for one handed, 15x for daggers, and 2x for anything else with the relevant perks (Deadly Aim, Backstab, Assassin's Blade)

I believe that any witnesses to the crime, even if they do not actually escape to tell anyone, cause you to gain a bounty.

Even if someone tells the guards, the guards will first go and check this. Maybe someone heard you after you entered, and ran to tell a guard, and then the guards saw the bodies. Or the people you killed were guards and it's automatically adds to you a bounty, and then even killing the guards won't help.