BANGOR, Maine — A man serving a three-year sentence in state prison for drug trafficking pleaded not guilty Monday in U.S. District Court to a charge that he threatened to kill President Barack Obama.

Leroy Eugene Dunn, 30, was indicted Jan. 12 by a federal grand jury for making threats against the president.

In April, Dunn allegedly wrote: “I hate you and will do anything I can to get rid of you. … You will die at my hands. … I will kill you Barack Obama.”

Dunn wrote the letter while being housed at the Piscataquis County Jail in Dover-Foxcroft while the drug trafficking case in Penobscot County was pending, according to Assistant U.S. Attorney James Moore, who is prosecuting the case.

Last fall, Dunn pleaded guilty in state court to threatening Gov. Paul LePage. He was sentenced to 60 days in jail to be served concurrently with a three-year sentence for drug trafficking.

Dunn’s mother, Philomena Gordon of Bingham, has said that her son is mentally disabled and also suffers from the effects of Marfan syndrome, a disorder of the body’s connective tissues that can result in disproportionately long arms and legs, among other symptoms.

Gordon said her son stands 7 feet, 6 inches tall and weighs more than 300 pounds. She told the Lewiston Sun Journal last week that Dunn should be under supervised medical and psychiatric care, not behind bars.

If convicted, Dunn face up to five years in federal prison and a fine of $250,000.