ORLANDO, Fla. (AP) — A Florida man has been convicted of leaving threatening voicemails for U.S. Sen. Bernie Sanders.

Court records show that a federal jury in Orlando found 57-year-old Robert Francis Pratersch guilty Tuesday of threatening a federal official and interstate transmission of a threat to injure. He faces up to 15 years in prison at a July 16 sentencing.

Federal prosecutors say Pratersch left three profanity-laced, anti-Semitic voicemail messages last fall at Sanders's office in Burlington, Vermont. Authorities say Pratersch threatened to behead Sanders, "ISIS-style," and videotape the execution. The remark was a reference to the Islamic State militant group.

Pratersch was indicted by a federal grand jury in February and arrested later that month in St. Cloud, Florida.

Sanders is seeking the Democratic presidential nomination.