Why the scare ?.
Humanity has a track record going back many thousands of years in implementing the most horrific ways of killing other humans in wars and other conflicts.
So why the scare ?, someone inventing a robot capable of doing what humans do to each other would be a pretty sick person, and it would probably not pass a quality review in the company he is designing the robot for.
The only law on robots we need is that they are not allowed to have capabilities which enable self replication. For the rest, it is hard to imagine someone could make a robot which can not be reduced to rubble by humans using a WW2 era Rheinmetall 88mm flak, or better.