MASSILLON, Ohio -- A 15-year-old Massillon student is in custody at a juvenile detention center, accused of groping a teacher in a women's restroom.

Authorities said the Massillon Middle School student stalked the teacher, waiting outside the bathroom and then following her inside, and the incident was captured on surveillance video, reported NewsChannel5's Jonathan Costen.

The video showed the student run down the hall, passing a substitute teacher and then turning around. The boys' bathroom is on the left, and the teacher is seen going into the women's room on the right.

Sex crime Detective Bobby Grizzard said the boy patiently waited to make his move.

"My theory is you're going to see his shadow. I believe he's waiting to hear the toilet flush," said Grizzard.

Police said the student then went into the women's room and stayed in there for about 20 seconds. Authorities said the teacher was confused, wondering if she went to the wrong bathroom.

Police said the student grabbed the teacher's buttocks.

"She said, 'What are you doing? I'm a teacher.' He said, 'Oh, I thought you were a student,' and it doesn't make any difference, it's wrong if it's a teacher or a student," said Grizzard.

Grizzard said in his 15 years experience of working sex crimes, he's never heard of a student groping a teacher.

"This is a young man. With his history, he'll be heading down the path of prison if he doesn't do something between then and now in terms of grabbing females," said Grizzard.

Police said the seventh-grader was in the Massillon school system for only a couple of weeks.

Grazzard said he came from the Tallmadge school system, where he had four reported cases of groping students.

He is in custody and the school superintendent said he may be expelled.