Updated

Authorities say two teenage girls in southern Maryland tormented a boy with diminished mental capacity, coerced him into sexual acts and made video recordings of the abuse.

Seventeen-year-old Lauren Bush of Mechanicsville is charged as an adult with assault, false imprisonment and solicitation for child pornography. She was released Tuesday.

An unidentified 15-year-old is charged as a juvenile. She's being held by the Department of Juvenile Services.

Sgt. Cara Grumbles says the boy's parents tell police the 16-year-old is autistic. All three teens attended Chopticon High School.

She says the girls assaulted the boy with a knife, kicked him in the groin and dragged him by his hair.

She says they also made him walk on a partly frozen pond, and wouldn't help him when he fell in.