Evil Artifact Makes Students Possessed, Twist Ending

by Barbara
(Long Island, New York, USA)

Hi there. A good movie came out in the late 90's or early 2000's about two guys that purchase an artifact / wooden box at an antique shop.

There are evil powers in the box and some students become possessed. At the end, they are all at a summer home and a struggle ensues. It turns out that it was one of the teachers who was responsible for killing the students throughout the movie.

Any help you can give me would be greatly appreciated!