It is believed that many of the murders are the work of multiple serial killers. Most of the victims were aged 12–25 years. Some shared similar physical features, such as similar hairstyles.[3] Despite efforts by the League City, Texas police, along with the assistance of the FBI, very few of these murders have been solved, and those that have been solved were predicated on confessions given by prisoners, or confessions given under duress from the police. [citation needed]