Cause of death: heart attack
Ole Kirk Christiansen (born Ole Kirk Kristiansen; 7 April 1891 – 11 March 1958) was a Danish carpenter. In 1932, he founded the construction toy company Lego, later known as The Lego Group. Christiansen transformed his small woodworking shop, which initially sold household products, into a manufacturer of wooden toys. By 1934, he had officially named the company Lego and established its fundamental principles. The business shifted to producing plastic bricks after the acquisition of a plastic moulding injection machine in 1947. Following his death in 1958, the company's management was handed over to his son, Godtfred.
Source : Wikipedia