Two men were shot — one seriously injured — near Chestnut Street and Washington Avenue in Chelsea on Saturday afternoon, police said. A pair of men opened fire on the victims, then fled, Chelsea Police Captain Keith Houghton said. One of the victims was struck twice and was taken to Massachusetts General Hospital. The other suffered an injury not believed to be life-threatening and was not hospitalized, police said. The shooting was not random, Houghton said, and one of the victims is known by officers for his police record.