A pretty standard hydraulic trencher. Have you ever seen one? They’re serious business, and you should absolutely, under no circumstances, step away from the controls while it is running. He shouldn’t have been using it in the first place, but even if he was, he should have been told that. Repeatedly. With great emphasis, and accompanied with graphic descriptions of what can happen if you don’t respect the machine. From the report it sounds like he got a brief overview and someone maybe watched him using it for a couple hours. Then they told him to work it by himself with no supervision the next day.