As reported by engadget,
The gaming world recently lost one of its most quietly influential figures. The Wall Street Journal has learned that Microsoft engineer Eric Engstrom died on December 1st at the age of 55 from complications following an injury. Engstrom, along with Alex St. John and Craig Eisler, played a key role in developing DirectX — the programming interface that made serious Windows gaming viable and cleared a path for the Xbox.
St. John tapped Engstrom in 1994 to help make gaming in the upcoming Windows 95 operating system practical. At the time, developers preferred the low overhead and greater control DOS offered over Windows 3.1. In addition to working on the project, Engstrom helped St. John advocate for the eventual DirectX platform despite a lack of support from Microsoft itself. Windows leader Brad Silverberg even had to fight to keep Engstrom, St. John and Eisler employed.