The soldiers stand at attention outside of (presumably) their barracks with white officers. I am not entirely certain this is the coast artillery regiment, but may be another unit assigned in the nearby area photographed by Pfc. Foronda.
This is a M1906 "disappearing gun" which may still be in the same emplacement at Fort Mills or Fort Wint. This is likely the same crew that Pfc. Foronda was a member of.