WARNING: The details in this article are graphic in nature and may be upsetting to some readers.

ROCKLAND, Maine (NEWS CENTER) -- A Rockland man has pleaded guilty to charges of aggravated assault and endangering the welfare of a child.

According to an affidavit, Douglas Merrifield entered a guilty plea on October 14 for an incident back in June.

Merrifield's wife showed a Knox County detective a video more than an hour long of the alleged abuse, according to the affidavit.

It also says the first ten minutes of the video shows Merrifield choking his son six times. In one of the chokings, the boy is seen convulsing. It also shows Merrifield repeatedly knee striking the boy, including strikes to the groin, stomach, and legs. Merrifield is seen knocking him to the ground with the boy crying and whimpering in pain. The final 50 minutes shows the boy standing with his head against the wall.

At some points in the video, the wife is seen interrupting the attack, but the attack resumes when she leaves the frame, according to the affidavit.

Court documents show Merrifield admitted to the assault in an interview with detectives, but blamed the attack on child's behavior saying, "sometimes when they are out of control I can get a little overly (unintelligible) with him."

Merrifield is set to be sentenced in December.