A documentary about the stabbing of a Waukesha girl in an effort to please a fictional character called Slenderman is due out next year.
HBO released a trailer for the documentary called "Beware the Slenderman" on Thursday and said the film will premiere Jan. 23.
Two teenage girls are accused of luring Payton Leutner, 13 at the time, into a wooded area in Waukesha in May 2014 and stabbing her 19 times. Payton survived the attack, and the two girls accused in the case were charged as adults with attempted first-degree intentional homicide in the attack.
The girls claimed they attacked Payton as a sacrifice to the horror character called Slenderman.