WARNING | This story contains disturbing content.

Disturbing footage captured by a hidden camera was part of the tip to police before the arrest of a Gatineau, Que., man accused of abusing his girlfriend's eight-year old boy, who has autism.

The boy is non-verbal, but his mother suspected something was wrong when she noticed her son swaying more vigorously and making higher pitched whimpers when her boyfriend was around.

The child's change in behaviour led his mother to hide her cell phone in a basket of laundry and hit the record button while she went out on an errand.

The boy's uncle said what was captured on that cell phone has traumatized the family.

In order to protect the identity of the child, CBC is not naming any family members in this story.

"She's 27 years old — that's her only child," said the uncle. "She put her trust in someone with the most important thing in her life, that trust was broken and that child was hurt. She's not OK."

He said his nephew used to like being tickled and hugged, but now flinches when he is embraced. Recently, his sister told him his nephew has started to violently shake in his sleep.

"I just want to protect him like my own kid," said the uncle.

"He's going to be different now and that kills everyone in the family."

Disturbing footage

CBC has viewed the thirty-minute video which shows the abuse getting progressively worse.

A man is seen hitting a boy in the mouth and slapping him in the head when the child whimpers.

The man also places his hands around the boy's neck and shoves him onto the couch.

At one point, the man changes the eight-year old's diaper and orders the boy to throw the used diaper away. When the child doesn't, the man rubs the dirty diaper in the child's face.

The uncle said as soon as his sister viewed the footage, she packed her belongings and ran away from the boyfriend.

The uncle sent the video of the alleged abuse to Gatineau police on Jan. 15. Yesterday morning, police arrested Adam Wilkins, 36, at his home.

Wilkins has been charged with one count each of sexual assault, assault and assault with a weapon.

He is in custody and will make another court appearance next week.