The video of the little boy running on a treadmill is horrifying to watch.

But jurors in the murder trial of his father, Christopher Gregor, 31, currently underway in Toms River, New Jersey, had no choice: They were required to see the surveillance footage of the New Jersey gym where prosecutors said Gregor forced his 6-year-old son, Corey Micciolo, to run at high speeds even as the boy struggled to find his footing and fell off the moving belt.

The video shows Corey falling six times, sliding on his back and face-first behind the treadmill. Each time, his father picks him up, at one pointing seeming to bite the boys head as he tries to stay upright. Eventually Gregor appears to slow the speed and Corey resumes running until his father stops the machine and the two walk out of the gym.

Thirteen days later, on April 2, 2021, the boy was dead.