BBC News Link (Inserting URL leads to a blank media glitch.) The world's biggest investment management firm is stepping up pressure on companies that make and sell guns after the Florida school shooting. BlackRock Inc is considering offering investors the chance not to invest in gun firms, and is asking those firms how they monitor safe use of weapons. The US corporation said the Florida shooting on 14 February, in which 17 people died, required a response. It is the largest shareholder in two of the biggest US gun manufacturers. "As it has for many people, the recent tragedy in Florida has driven home for BlackRock the terrible toll from gun violence in America," the corporation said on its website. "We believe that this event requires response and action from a wide range of entities across both the public and private sectors." What is BlackRock Inc? It is the world's largest fund manager. BlackRock manages more than £4 trillion ($5 trillion) worth of investments and pension funds worldwide and is often consulted by governments. The company is the largest shareholder in leading gun makers Sturm, Ruger & Co and American Outdoor Brands (formerly Smith & Wesson). BlackRock is also a large shareholder in firms such as Walmart and Dick's Sporting Goods which sell guns. But these shares represent a tiny fraction of its total assets.