A rising star left hedge fund powerhouse DE Shaw after the firm determined he had violated its risk guidelines, according to people close to the matter, a sign of how Wall Street firms have moved to curb risks and rein in even their biggest moneymakers.

Parvinder Thiara, a 30-year-old graduate of Harvard University and a Rhodes scholar, left late last year after helping DE Shaw's "macro" group rack up hundreds of millions of dollars in profits in recent years, the people said.