The U.S. Secret Service is investigating presumptive Republican presidential nominee Donald Trump's former butler over a Facebook post calling for President Barack Obama's assassination.

The former butler, Anthony Senecal, 74, said in a Facebook post Obama should be hanged for treason. He made the statement in 2015, and the magazine Mother Jones wrote on Thursday about the post and other similar remarks by Senecal. Senecal worked for decades as a butler at Trump's Palm Beach mansion, Mar-a-Lago.

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After reports of Senecal's comments began to circulate, the Secret Service said in a statement, "The U.S. Secret Service is aware of this matter and will conduct the appropriate investigation."

The story broke as Trump, whose proposals to ban Muslims from entering the United States and build a wall along the Mexican border have drawn heavy criticism, concluded a charm offensive on Capitol Hill. He attended a series of meetings there on Thursday with Republican lawmakers to try to win the party establishment's support for his candidacy.

Senecal has not served as a butler to the billionaire candidate since 2009, but he was identified in a March 15 profile in the New York Times as a current employee of Mar-a-Lago, serving as the estate's historian.

Hope Hicks, a spokeswoman for Trump, said in a statement, "Senecal has not worked at Mar-a-Lago for years, but nevertheless we totally and completely disavow the horrible statements made by him regarding the president."

She declined to comment on the Times report about Senecal's recent role. Senecal did not respond to a call seeking comment and could not be reached by email.

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"It is time for our Military to drag that fraud out of the white mosque and hang his ass for treason and other high crimes against AMERICA !!!!!!!" Senecal wrote on Sept. 13, 2015, in reference to Obama.

Mother Jones reached Senecal on Thursday. The magazine reported that Senecal said of his Facebook comments, including a private comment on Wednesday in which he said Obama should be shot: "I wrote that. I believe that."