Scott Gottlieb, the commissioner of the Food and Drug Administration (FDA) who sounded the alarm on teen vaping, unexpectedly submitted his resignation after nearly two years at his post. The administration announced his departure Tuesday afternoon.

Gottlieb has filed paperwork to resign but "will be on for at least another month," an administration official told CBS News. It's unclear who will take Gottlieb's place.

"Scott has helped us to lower drug prices, get a record number of generic drugs approved and onto the market, and so many other things. He and his talents will be greatly missed!" President Trump tweeted.

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Health and Human Services Secretary Alex Azar said Gottlieb "inspired historic results" from the FDA on affordable generic drugs and advancing policies on opioid addictions and e-cigarette use.

"All of us at HHS are proud of the remarkable work Commissioner Gottlieb has done at the FDA," Azar said in a statement. "He has been an exemplary public health leader, aggressive advocate for American patients, and passionate promoter of innovation. I will personally miss working with Scott on the important goals we share, and I know that is true for so many other members of the HHS family."

Dr. Scott Gottlieb seen Oct. 25, 2017, in Washington. Getty

During his tenure, Gottlieb also dealt with the consequences of the longest government shutdown on record, halting some food inspections due to a lack of personnel and resources and then working to bring those inspections back online as the shutdown continued.

In September, Gottlieb called teen vaping an "epidemic" and vowed to crack down on companies that market to minors.

"The disturbing and accelerating trajectory of use we're seeing in youth, and the resulting path to addiction, must end. It's simply not tolerable," Gottlieb said. "I'll be clear. The FDA won't tolerate a whole generation of young people becoming addicted to nicotine as a tradeoff for enabling adults to have unfettered access to these same products."

Before becoming FDA commissioner, Gottlieb worked in the health care and pharmaceutical industries, and served on the board of a company that sold vaping products.

This is a developing story and will be updated.