JACKSONVILLE, Fla. (AP) -- An internal investigation is planned at the Jacksonville Sheriff's Office after one of its detectives resigned for making threatening comments about President Barack Obama.

Sheriff John Rutherford told The Florida times-Union the remarks made by detective Sam Koivisto were not a legitimate threat, but they were unacceptable workplace conduct.

The U.S. Secret Service is also investigating.

Koivisto was a 26-year veteran with the sheriff's office. He quit in the face of the internal affairs probe following his statements about the election. Comments were also made about the Democratic Party.

Authorities have not released further details about the comments made. Koivisto could not be reached for comment.