The co-head of Blackstone’s big hedge-fund unit plans to leave the firm as the private equity giant seeks higher returns and faster growth for the business.

Blackstone veteran John McCormick told the firm last week he had decided to resign, the firm told The Wall Street Journal. His co-head, former Brown University endowment chief and hedge-fund manager Joseph Dowling, who joined the firm in January, will become sole head of Blackstone Alternative Asset Management, the world’s largest funds-of-hedge-funds business.