A small group of 10 or so scientists, well funded by a nation state could absolutely do it, and absolutely keep it secret I have friends who are working on kil

A small group of 10 or so scientists, well funded by a nation state could absolutely do it, and absolutely keep it secret I have friends who are working on killer robots (terminator style) and they are not interested in fame or notoriety, they want the technical challenge and the fat paycheque. Whether you agree with the ethics of this is irrelevant, the point is, it can be done