Dreams involving violence, especially those that include themes of murder and captivity, can be quite distressing. They often reflect deep-seated fears, anxieties, or feelings of powerlessness in your waking life. Here are some possible interpretations of your dream:

1. Fear of Betrayal or Danger: The presence of the girl you thought was a friend and the sudden violence may symbolize a fear of betrayal or unexpected danger in your relationships. This could reflect concerns about trust and safety in your life.
2. Feelings of Powerlessness: Being held hostage and having to cater to the murderer may indicate feelings of powerlessness or being trapped in a situation in your waking life. This could relate to a relationship, job, or personal circumstance where you feel you have little control.
3. Inner Conflict: The violent acts may represent inner conflicts or unresolved issues that you are grappling with. This could manifest as repressed emotions or situations that are causing you distress.
4. Need for Protection: The dream may be urging you to seek protection or to establish boundaries in your life. It could be a sign to evaluate your relationships and ensure that you surround yourself with supportive individuals.
5. Processing Trauma: If you have experienced trauma or violence in your past, this dream could be a way for your subconscious to process those experiences.

Consider reflecting on any current situations or relationships that may be causing you stress or anxiety. It can be helpful to talk to someone you trust about these feelings or even seek professional guidance if the dream continues to trouble you. Remember, dreams can be a mirror of our concerns and emotions, and understanding them can lead to personal growth.