Josh Birnbaum, who helped orchestrate Goldman Sachs’ highly-profitable bets against subprime mortgage-backed bonds, has left the firm to found his own hedge fund.

Birnbaum, who was a managing director at Goldman, plans to raise about $1 billion for the fund, Bloomberg News reports. The fund is expected to join a glut of other vehicles pouring into mortgage investing in the wake of the continuing credit crisis.

Birnbaum joined Goldman in 1993 and reportedly made between $5 million and $15 million last year.