Robert --

This may be a case of mistaken identity. Simkins was involved in the incident, but as a cadet, not a colonel. The cadet who pulled the lanyard was George Haynesworth rather than Simkins.

For sources on this incident, see the following:

http://www.clansinclairsc.org/First-last%20shot.htm

Sgt. S. E. Welch, "The Citadel Cadets and the 'Star of the West'" (typed MS, n.d.), Hinson Collection, Charleston Library Society, Charleston SC.

Gary R. Baker, Cadets in Gray (Columbia, S.C.: Palmetto Bookworks, 1989).

The Siege of Charleston 1861-1865 (Columbia, S.C.: University of South Carolina Press, fifth printing, 1987).

H. M. Clarkson, "Story of the Star of the West," Confederate Veteran, vol. 21 (May 1913), p. 235.

The Citadel still has a "Star of the West" award for cadets:
http://www.citadel.edu/r3/about/tour/x/star.shtml