An 18-year-old from Minnesota remains in custody after a federal judge ruled he must stay jailed. Prosecutors claim the teenager plotted a terror attack at the Mall of America. The youth was arrested after purchasing an AK-47 from an undercover FBI agent. The judge denied bail. The case involves federal charges. The FBI conducted the undercover operation. The teenager is expected to face trial. The Mall of America is a major shopping center. The decision follows a court hearing. The judge cited the seriousness of the charges. The teenager has no prior criminal record. The FBI is investigating the plot. The case highlights concerns about gun access. The court emphasized public safety. The ruling was made in Minneapolis. The teenager is from the state of Minnesota. The case is under federal jurisdiction. The FBI is working with local authorities. The plot was uncovered through surveillance. The teenager was detained last year. The case is ongoing.