In order to attract the operation of the section quoted above with special, reference to the portions relevant to these cases, it is necessary (1) that the Commissioner, the District Magistrate or the Sub Divisional Magistrate specially empowered by the State Government in that behalf, as the case may be, should be satisfied that the movements or acts of any person are causing or calculated to, cause alarm, danger or harm to person or property, or that there are reasonable grounds for believing that such person is engaged or is about to be engaged in the commission of an offence involving force of violence or an offence punishable under Chapter XII, XVI or XVII, Indian Penal Code, or in the abetment of any such offence, and (2) that in the opinion of such officer witnesses are not willing to come forward to give evidence in public against such person by reason of apprehension on their parts as regards the safety of their person or property.