Jim Frederick, the former top editor at Time who wrote one of the more critically acclaimed books on the Iraq War, died suddenly in Oakland, on July 31. He was 42.

Frederick died at the Alta Bates Summit Medical Center. The Oakland coroner’s office on Friday did not yet list a cause of death but said it was believed to be natural causes.

The veteran editor wrote the best-selling “Black Hearts: One Platoon’s Descent into Madness in Iraq’s Triangle of Death” in 2010.

He started his Time Inc. career at Money and rose to become the managing editor of Time.com and later the editor of Time International.

He met his wife, Time senior editor Charlotte Greensit, when he was stationed in London.

Frederick left Time Inc. about a year ago and had spent a year traveling the world with Charlotte before settling in San Francisco to start a new company, Hybrid Vigor Media.

Time’s managing editor, Nancy Gibbs, said in a memo to staffers on Friday, “All of us who got to work with Jim have wonderful memories of his collegial style, rigorous standards and profound commitment to the very best of Time’s values.”