There are already robots that can throw the ball or juggle (on their own). This creation from Disney Research can quite successfully throw the ball together with a living person.
Both Microsoft Kinect and ASUS Xtion Pro Live are mentioned as used technologies. ')
The robot tracks the movements of a person in order to catch the ball and throw it back, and most often it succeeds quite well. If the ball is not caught, the robot can shrug and look after him.
Also on the video you can see the attempts of people to juggle with the robot.
The company intends to bring the interaction with people to the mind and place such robots in the Disneyland.
Of course, if we talk about Robokalipses and Skynet, you can begin to make assumptions which of these companies will be responsible for throwing live targets with grenades.