“The detection of an unbounded wall should ring an alarm bell,” he said. Did he fear something will collapse on him? Another court-appointed expert, Mario Buttigieg, testified about his conclusions after examining the accident site and finding the “hammer of the hymac [construction machinery] inserted in the rock, literally speaking.” Tracks on the ground indicated the semi-circular trajectory taken by the hydraulic excavator as it turned backwards, away from the wall beneath the Pace residence to the opposite side of the construction site. Buttigieg said that footage capturing the moment of the incident showed that as the machine was about to move backwards, the building collapsed.