BlackRock, Youtube
He was one of the original team that started what is now the world's largest asset manager, responsible for $4.7 trillion (£3.06 trillion) of investments, and started the company's crucial Aladdin (Asset Liability and Debt and Derivative Investment Network) platform.
Aladdin is one of the most dominant platforms for investment and risk management in the world today, and it was all started by Hallac.
BlackRock's release explains just how important he was to the firm's astonishing growth: "He purchased the firm's first computer server, placing it between the coffee machine and refrigerator in the firm's one-room office."
Back in 1988 the business operated from one room, and he was the company's first actual employee.
In a late 2013 piece, the Economist explained just how far the system reaches - it's used much more widely than just by BlackRock:
"Aladdin", the risk-management platform that occupies all those computers in the orchards, is not just used to look after BlackRock's $4 trillion. The firm makes its facilities available in whole or in part to managers looking after $11 trillion more, a tally that has recently been growing by about $1 trillion a year. All told, Aladdin keeps its eyes on almost 7% of the world's $225 trillion of financial assets.
Here's a video produced by BlackRock two years ago explaining the importance of Aladdin, and calling it the company's "central nervous system," and featuring Hallac:
Larry Fink, BlackRock's chairman and CEO paid tribute to Hallace in a press release: "He was a visionary who embodied our culture and was truly the heart and soul ofBlackRock. His extraordinary innovations, including our unique Aladdin platform, have been central to our success."