Longtime Apple Valley Fire Chief Nealon Thompson resigned in late October after the city determined he had engaged in repeated sexual contact with a lower-ranking city employee, according to city records.

Last April, Thompson contacted city leadership to report his own “unprofessional conduct.” City Administrator Tom Lawell put Thompson on paid administrative leave while officials investigated.

In late August, the city told Thompson that he might be disciplined or fired because the investigation had confirmed his sexual contact with the city employee.

That contact violated several policies in the city’s personnel handbook, including one related to ethical and professional behavior and another related to discrimination and harassment.

In a letter to Thompson obtained through a Star Tribune data practices request, Lawell said that when a department head has sexual contact with a subordinate employee, the power differential between the two means the employee feels pressured to allow the interactions to occur.

The pair’s relationship and the conflict that followed kept the lower-ranking employee from coming to work and led to other employees not being able or willing to work with Thompson, the letter said.

Thompson resigned on Oct. 24. He had signed a separation agreement earlier in October, in which the city agreed to pay him for unused vacation time.

Deputy Fire Chief Chuck Russell, who had already been serving as the acting fire chief, will continue in that role until the city picks a new leader, the city said.

Thompson joined the department in 1991 and was promoted to acting chief in 2008. He became chief in 2009.

He could not be reached for comment Wednesday.

The city’s fire department has 62 paid on-call firefighters, five full-time employees and a part-time secretary.