Peter Peterson, who co-founded the private-equity giant Blackstone Group BX, +0.29% after having helmed Bell & Howell and Lehman Bros. as chief executive, has died at the age of 91, the Associated Press reported, citing family members.

Peterson founded Blackstone in 1985 with Stephen Schwarzman, who remains chairman and CEO. The firm says it has $434 billion under management as of late 2017. Peterson retired as senior chairman in 2008.

Peterson served as commerce secretary under President Richard M. Nixon.

Blackstone co-founder Peter G. Peterson, the Nebraska-born son of Greek immigrants, speaks of “the American dream” of upward mobility during a 2012 event organized by the Atlantic magazine.

Peterson’s Peter G. Peterson Foundation has focused on revamping government entitlement programs including Medicare and Social Security, and he was a prominent voice among those espousing efforts to “fix the debt.” In 2012, the Los Angeles Times called him the most politically influential American billionaire.

Blackstone co-founder Peterson dead at 91: report