How did mad eye described the disturbance in his yard?

Alastor 'Mad-Eye' Moody didn't actually explain the disturbance, because the disturbance was him being captured by Barty Crouch Jr. Barty promptly took Polyjuice potion transforming himself into Moody.

Moody's dustbins were a deterrent against intruders and were set to fire rubbish in the air. The muggle police were baffled when they arrived, and Arthur Weasley was sent to solve the situation. Crouch (appearing as Moody) didn't have to explain much as it was well known that he was very paranoid.