Mohammad Barkindo, the secretary-general of OPEC, passed away suddenly on Tuesday night, only hours after visiting Nigerian President Muhammadu Buhari and speaking at an energy summit in Abuja, Nigeria, according to the Wall Street Journal.

After serving as the senior official of the Organization of the Petroleum Exporting Countries for six years, Barkindo, 63, was scheduled to step down at the end of July. He gained notoriety for drafting a 2016 accord that welcomed major producers like Russia into the so-called OPEC+ club, which included them as heavyweight producers.

“We lost our esteemed Dr. Muhammad Sanusi Barkindo,” Nigerian National Petroleum Corp (NNPC) CEO Mele Kyari tweeted. The death is a “great loss to his immediate family, the NNPC, our country Nigeria, the OPEC, and the global energy community,” Kyari added.

We lost our esteemed Dr Muhammad Sanusi Barkindo. He died at about 11pm yesterday 5th July 2022. Certainly a great loss to his immediate family, the NNPC, our country Nigeria, the OPEC and the global energy community. Burial arrangements will be announced shortly.

— Mele Kyari, OFR (@MKKyari) July 6, 2022

The native of Nigeria claimed during his speech in Abuja that the oil and gas sector is currently “under siege” and suffering from significant underinvestment.

“In a very short timespan, the industry has been hit by two major cycles — the severe market downturn in 2015 and 2016, and the even more far-reaching impact of the Covid-19 pandemic,” Barkindo said hours before his death.

Barkindo was scheduled to join the Atlantic Council, a US-based think tank, as a distinguished fellow in the Global Energy Center after leaving OPEC. On July 31, his tenure as OPEC secretariat came to an end, and Haitham Al-Ghais of Kuwait will take over.

“This tragedy is a shock to the OPEC Family. We express our sorrow and deep gratitude for the over 40 years of selfless service that Mohammad Sanusi Barkindo gave to OPEC. His dedication and leadership will inspire OPEC for many years to come,” the OPEC Secretariat said in a Tweet.

This tragedy is a shock to the OPEC Family. We express our sorrow and deep gratitude for the over 40 years of selfless service that Mohammad Sanusi Barkindo gave to OPEC. His dedication and leadership will inspire OPEC for many years to come.

— OPEC (@OPECSecretariat) July 6, 2022