CANADIAN COUNTY, Oklahoma - The Canadian County Sheriff confirms a deputy was fired for having personal financial engagements with someone he was investigating.

Lieutenant Ken Thompson was terminated in September. Through the Oklahoma Open Records Act, News 9 received the four-page termination letter on Tuesday.

Sheriff Chris West says Ken Thompson was with the Canadian County Sheriff’s Office for 14 years and was one of the investigators.

“When someone takes a job in law enforcement, that’s a position of public trust,” said the sheriff.

West writes in the letter that Thompson made a “personal financial transaction”, which links back to an organized theft ring the lieutenant was investigating.

In August 2017, the note says Thompson wrote a personal check for a $4,300 air-conditioning system, but he got at $1,500 discount from Theodore Gatlin, the owner of a local heat and air business.

Sheriff West said Gatlin was a “co-conspirator” in the theft ring involving Dennis Lee, a prominent Oklahoma home builder. This was something that Thompson discovered throughout his investigation, yet the lieutenant still chose to do a personal exchange with Gatlin.

The letter indicates Gatlin was never criminally indicted. He instead provided crucial evidence for the prosecution in Lee’s federal trial. Both Gatlin and Thompson would be key witnesses, but the sheriff writes that the personal engagement has “damaged the prosecutorial efforts.”

“You can’t be doing personal business with people that you’re investigating,” Sheriff West told News 9.

The termination letter reads, “Your conduct has brought shame and discredit on the Sheriff’s office and its hard working, honorable employees.”

West even notes that this isn’t the first time Thompson has disappointed him. Years ago when West was the undersheriff, Thompson was in a chase where he did thousands of dollars of damage to his unit. During the incident, West said Thompson failed to mention he fired his gun. He believed Thompson should have been terminated at that time, but the former sheriff decided otherwise.

He writes to Thompson, “You have violated the public trust and your conduct gives the appearance of public corruption. West fired Thompson on September 13, effective immediately.