Upon filing a petition with the court for an injunction pursuant to this chapter, the petitioner may obtain a temporary restraining order if the petitioner also files an affidavit that, to the satisfaction of the court, shows reasonable proof that an employee or employer has suffered unlawful violence or a credible threat of violence by the respondent and that great or irreparable harm will result to an employee or an employer if the injunction is not granted. The affidavit shall further show that the petitioner has conducted a reasonable investigation into the underlying facts that are the subject of the petition. A temporary restraining order granted under this chapter shall remain in effect, at the court's discretion, for a period not to exceed fifteen (15) days, unless otherwise modified or terminated by the court.