U.S. Surgeon General Vivek H. Murthy has been removed by the Trump administration and replaced temporarily by his deputy, Rear Adm. Sylvia Trent-Adams.

Murthy, a holdover from the Obama administration, was asked to resign, according to a statement released Friday night by the Department of Health and Human Services. The statement said “after assisting in a smooth transition into the new Trump administration” Murthy “has been relieved of his duties.” Trent-Adams, a 24-year veteran of the Public Health Service Corps and a former chief nurse officer of the public health service, will fill the role for now.

In a post on Facebook, Murthy wrote that “for the grandson of a poor farmer from India to be asked by the president to look out for the health of an entire nation was a humbling and uniquely American story. I will always be grateful to our country for welcoming my immigrant family nearly 40 years ago and giving me this opportunity to serve.”

A physician, Murthy, 39, is a longtime believer that gun violence is a public health issue, a view that stalled his nomination in the Senate for more than a year.

“The statements I’ve made in the past about gun violence being a public health issue, I stand by those comments because they’re a fact,” he said then.

His biggest accomplishment may have been the November 2016 publication of a landmark report on drug and alcohol addiction, which placed that condition alongside smoking and AIDS as public health crises. His office sent millions of letters to doctors asking for their help against the opioid epidemic and he labeled the matter “a moral test for America.”