My boyfriends ex threatened my life over the phone as well as told me she would make it so we couldn't be together and screw us both over. She also had a friend of hers threaten my boyfriend at the same time. We both contacted the police about it and filed reports, she was taken to the police station and released that same night. She was told to leave us both alone and that was it. The next day she went to the police with a story that he had held a gun to her a year ago, and said that we were the ones calling and threatening her. He is now being held in questioning for 5 days now. They refuse to release him because they can't prove that he doesn't have a gun, but she has no proof that any of this actually happened. What can I do? Or what can be done?

Get an attorney. First, it is basically illegal to hold someone for 5 days without charging them. Second, you sue the ex for harassment and filing a false police report.

Agree, assuming this is in the US, they can not legally hold him for 5 days, unless they have charged him officially with a crime ( unless he had warrants out for him for something else) Next after your complaints, it is very unlikely they would take the gun threat serious unless of course she had some proof of it.

He needs an attorney right now. Since they have either violated his rights, or you do not know the entire story