Bank of Canada Deputy Governor Sylvain Leduc will be leaving his post next month in an unexpected departure for one of the top policy makers at the central bank.

Leduc will return to the Federal Reserve Bank of San Francisco, where he worked before his appointment at the Ottawa-based bank in 2016, the Bank of Canada said in a statement. The Canadian central bank didn’t say why Leduc is departing from his post.

“Sylvain has been a wonderful addition to Governing Council. We have benefited from his policy expertise and his strong sense of teamwork,” Governor Stephen Poloz said in the statement. “Sylvain’s motivation and leadership has had a powerful impact on our researchers and on the Bank’s capacity as a research institution.”

Leduc is departing the key policy making body at a crucial time, with the Bank of Canada in the middle of a rate normalization process that has seen it already raise interest rates three times since the middle of last year. The central bank’s next rate decision -- and Leduc’s last -- will be July 11. Investors are almost fully pricing in another hike at that decision.

The bank said Leduc, who oversaw analysis and financial stability issues, will be leaving in “late” July. Before joining the Bank of Canada, Leduc served as vice president for microeconomic and macroeconomic research at the Sand Francisco Fed.

The Bank of Canada said the search for his replacement will begin immediately.