The man that fights the dragon is St George; the other one is Guifré el Pilós father, that defeated another dragon.
Legend has it the following way. The Saracens were not capable of defeating the Barcelona Counts. Thus they decide to retire, but they first sent an expedition to the northern African mountains. There they captured a young dragon that was set onboard a ship towards Barcelona. The dragon was unleashed in the Llobregat river mouth. Was taken inland, and released. The dragon found shelter in a place still known as the Cova del Drac (dragon cave).
At first the dragon ate lambs, but readily found pleasure in eating peasants and knights, whose armors would spit out like seeds. Nobody, not even Espes, a Catalan Knight with experience fighting against dragons in Africa, could kill the beast. Not even a squad of knightsmen could kill it. The dragon spat so much fire that they all fell off the Salt dels Cavalls (horse jump), a cliff still called this way today. At last the Catalans decided to burn the woods, but the dragon flew away taking shelter in Montserrat. Once the fire was off, the dragon came back to it’s cave in Sant Llorenç de Munt.