A sculptor, medallist and designer, Horejc trained in engraving at a school of jewellery before studying at the School of Applied Arts in Prague (1906−1910) where his teachers were Josef Drahoňovský and a Stanislav Sucharda. His sculptural works were influenced by classical Greek statuary, and because of their elegance and timelessness they were sought after by architects such as Jan Kotěra or Ladislav Machoň, who used them, for instance, for the building of the Ministry of Labour and Social Affairs in Prague (1929). From 1909 he collaborated with the Artěl association, for which he designed handcraft items. His glass vase designs achieved an international reputation. His sets of drinking glasses Bacchus, Prague, Land of Canaan, Dance and The Three Graces were awarded the 1925 Grand Prix at the International Exhibition of Decorative Arts in Paris. He also won prizes for his metalwork, such as the reliefs in the Comenius Museum at Naarden (1935−1937). Much sought-after was the jewellery he created out of pakfong, whose malleability enabled him to engrave fine and complex lines and create artistically individual items. His monumental works include numerous tomb statues and memorials, such as the monument to the fallen at Dvůr Králové (1922).