These exist and have been used by Israel in Gaza. At least for now a remote operator has to give the OK to shoot, but the drone does the targeting itself. It's

These exist and have been used by Israel in Gaza. At least for now a remote operator has to give the OK to shoot, but the drone does the targeting itself. It's very Terminator-esque, a quadcopter with an automatic rifle that can autonomously navigate streets, loiter, and identify and aim at human targets.