Whoever knowingly and willfully holds to involuntary servitude or sells into any condition of involuntary servitude, any other person for any term, or brings within the United States any person so held, shall be fined under this title or imprisoned not more than 20 years, or both. If death results from the violation of this section, or if the violation includes kidnapping or an attempt to kidnap, aggravated sexual abuse or the attempt to commit aggravated sexual abuse, or an attempt to kill, the defendant shall be fined under this title or imprisoned for any term of years or life, or both.