In the event of (a) war, insurrection, rebellion, invasion, tumult, riot or a mob, (b) a body of men acting together by force with intent to commit a felony, to offer violence to persons or property or by force and violence to break and resist the laws of this State or of the United States, (c) in case of the imminent danger of the occurrence of any of such events or (d) in the event of public disaster the Governor may order the National Guard of South Carolina or any part thereof into the active service of the State and cause them to perform such duty as he shall deem proper. The Governor may also upon the written request of the mayor of a city or the sheriff of a county within which a large public assemblage is to occur order out the National Guard or any part thereof to preserve order and keep people within bounds at such assemblage. In case the Governor shall be absent from the State or unavailable for any reason, the authority herein bestowed shall pass to the Adjutant General of the State.