A biologically relevant reactive sulfur species (RSS), the hypothiocyanite radical OSCN, is generated in the gas phase through flash vacuum pyrolysis (FVP) of trifluoromethyl sulfinyl cyanide CF3S(O)CN at ca. 1000 K. Upon UV light irradiation (365 nm), OSCN rearranges to novel isomers OSNC and SOCN, and further visible light irradiation (400 ± 20 nm) leads to reverse isomerization. The identification of OSCN, OSNC, and SOCN in cryogenic matrices (Ar and N2, 2.8 K) with IR spectroscopy is supported by quantum chemical calculations up to the CCSD(T)-F12/VTZ-F12 level. The potential energy surface for the interconversion of OSCN isomers and their bonding properties are computationally explored by using the CCSD(T)-F12/VTZ-F12 and EDA-NOCV methods, respectively.