ManTech International Corporation filed SEC Form 8-K: Termination of a Material Definitive Agreement, Completion of Acquisition or Disposition of Assets, Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing, Material Modification to Rights of Security Holders, Changes in Control of Registrant, Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Leadership Update, Other Events, Financial Statements and Exhibits