Watch out for children crossing

In an attempt to foster physical education in our children, we went to the courtyard of our apartment with two soccer balls.

While we were playing (I was really trying to enforce the "don't use your hands, use your feet"), I had a chance to side-kick the ball to Joey (who looked up from licking a rock). Then we heard it:

An awful screeching noise of tires and a "bump." Then Milo running at me. I knew what he did, and he knew what he did, so once I grabbed him, the hysterical crying started. Why?

Because Milo got on the golf cart (used for touring around the property) and it happened to be plugged in, and he happened to get on it and hit the gas, pushing it into the wall. The management ran out of the office, and the damage was only a few scuff marks on the wall.

I apologized, and wrestled Milo upstairs, where he dramatically threw himself onto Joey's bed, still crying.

Was it Milo's fault for stepping on the gas, when he's been repeatedly told in the past year NOT TO GET ON the cart? Or, was it management's fault for keeping the cart plugged in during the day, with (at least) four neighboring apartments having kids?

Or, it's everyone fault. Milo's still in his room, making vague threats and weird noises behind the door. And I'm not going to stop him. (I'm too embarrassed to go down and talk to the management, even though I could totally take them down.)