What is scary that it is technically quite possible to develop such a gun even for an individual. The most complex part is probably mount and motors, but that is a manageable problem.
Believe it or not there are even more terrifying things than that. How long until someone builds a rifle scope that can visualize Wifi RF reflection patterns in the same way a thermal scope can see infrared? The rifle scope using this technology could see right through walls. https://news.mit.edu/2018/artificial-intelligence-senses-peo...