There’s no such harpoon or hook gun logics behind it as i see. To me it looks like that they are just connecting two points (Ground - Robot) with a cable actors.
And depending on the number of cables attached to it the robot falls, and due to the animations it looks like its stuck.
I’d create an actor called (Arrow) and attach a Cable Component to it. When it hits a target, attach the actor to the hit actor, and then for the second shot i would just spawn a second actor and set the Cable component’s Attach End To / Other Actor property.