The 12-year-old honor roll student killed inside her Gaithersburg townhouse last week was stabbed to death and her body was found in the basement, Montgomery County police said Tuesday.

Police released no other new details in the investigation, which they said remains wide open as it reached its seventh day.

“We’re not able to classify this as a known or acquaintance-type crime, or a stranger-based event,” said Capt. Paul Starks, a police spokesman. “This crime is a tragedy.”

Detectives believe someone killed Jessica Nguyen sometime in the afternoon or early evening of May 31 in the home she shared with extended family members.

Police have said she suffered trauma to the upper portion of her body.