Wrong idea if you want to be a pure thief, a theif would run in this situation. Now I'm not saying a theif wont kill, but killing is not a thiefs intention.
It's true that a thief's intention isn't about killing in order to thieve but the definition of thievery is taking what isn't yours which is what I would be doing. Don't get me wrong, my intention wouldn't be to kill them in order to get what they have. That for one keeps me from stealing from them again if they get anything else and 2 because it takes too much energy and time to kill them just to steal. However, with that being said, it would take even more energy and time to run from them if they find me stealing from them, then run from the guards who find me, pay off the guard or do the time. Much more simple to kill and cut my losses....or gains. But I agree, their shouldn't be the intention of killing the stolen from.