How would autonomous killing be precisely defined? Whenever a machine is designed to kill without an affirmative command from a human operator? Would that include landminds? Maybe it should...
A landmine is indiscriminate, by that logic anything with a triggerable fuze is autonomous (even a snare trap would be). The difference would be if the landmine chose to explode based on some other factor.
Autonomy and intelligence are not the same thing.
Autonomy gets truly dangerous because you dont need to create death zones and no mans land. They are not a less violent version of just bombing the area. They can run considerations and decide by themselves who to kill and with this, their usage outside of active front lines will be considered. And with that, the people deploying them give up the decision and delegate it to an algorithm or worse yet, a trained black box. Reality will be to have completely unaccountable killers bots flying over countries who cant defend themselves against foreign aggression.
This stuff has absolutely horrible potential and i find it prudent to shame and cut out anyone with a sufficient lack of a spine to work in this area. As unpopular as it is to consider the impact of the technology you are developing, it is taught for a reason in a CS degree. This work has the potential to screw over humanity for a while to come.
There have already been cases of "autonomous" targeting, such as in 1982 when Exocet missiles fired by Argentine aircraft at a British warship selected a cargo ship instead (possibly due to countermeasures used by the warship). In this case, the weapon hit a target not intended by the firing unit. Of course, unguided weapons do this all the time...
The combination of the two is interesting. The Mark 60 CAPTOR is a naval mine that launches an acoustically guided Mark 46 torpedo.