I feel very sorry for the boy and his family. My grandfather was killed the same way. He hooked onto the drawbar on his farmall cub with a chain that was hooked up to an old wooden bridge. He was going to pull it out to a wash out in the camp road so he could get my crippled aunt into the camp. Dad was the last one to see him alive as he was hooked on when dad said see ya later. Dad had to walk about 1/2 mile out to get back to the car. So everyone thinks gramp was dead before dad got out to the car. The tractor walked out from under gramp when he let the clutch out. He was hooked onto the 3 pt. hitch drawbar and it was in the upper position. When the tractor got going up you can't throw the clutch because of your body position. Dad had to go in and find him because my uncle didn't know where to look. They found him with the tractor on him, had to take a backhoe and lift it off him. Dr. said he didn't last anytime after it happened thank god for that. Gramp had just started letting me Harrow the pasture with it before he died, I never did see the tractor after that, Grammy sold it.
So just be safe out there on your equipment.
Rick