MINNEAPOLIS (AP) -- A Minnesota county sheriff who resigned unexpectedly last month is accused of threatening a female employee in the sheriff's office.

An investigation ordered by the Chisago County Attorney's Office shows that Rick Duncan wrote threatening letters last fall directing the employee to go with him to a training session in Bemidji and stay overnight at a hotel together or risk harm to their families. He allegedly directed the woman to refrain from telling her husband or reporting the matter to law enforcement or others.

The woman ultimately refused to go and months later reported the ordeal to a supervisor.

Duncan cited medical issues when he resigned last month. His attorney, Marshall Tanick, says Duncan is dealing with those issues.

Duncan could face criminal charges.