The Larimer County Sheriff's Office says they're still seeking more information about the killing of 28-year-old Andrea Bartmess. Larimer County Sheriff Justin Smith calls the case "a complicated puzzle."
The fifth person arrested was 21-year-old Chataigner McCaffrey-Pickett. Four others face murder charges.
KUSA-TV reports that Bartmess was diagnosed with bipolar disorder and had been living in a hotel in Fort Collins. Her mother reported her missing in mid-November, and Bartmess' body was discovered Nov. 21 near the northern Colorado town of Livermore. Investigators have not released a possible motive.
Authorities say they are still investigating the cause of death.