Martin Jansen was a man who was responsible for kidnapping Laurie Niles's daughter, Sarah in order to get Laurie to transfer some money to his bank account, presumably in exchange for her daughter's life. He and his partner, Rebecca Biddle who pretended to be Laurie's "sister" brought Laurie to the bank so that the transfer could go ahead. He attempted to kill Laurie but NCIS Special Agents Leroy Jethro Gibbs and Timothy McGee, having seen what was happening broke cover and shot Jansen, killing him instantly.