(CNN) The gunman who killed an officer in Northern California left behind a letter accusing the Davis police department of hitting him with "ultra sonic waves."

A man on a bicycle shot Davis police Officer Natalie Corona, 22, Thursday night as she responded to a triple-car crash in the city of Davis. He was later found dead with a self-inflicted gunshot wound.

In a statement Saturday, the Yolo County Sheriff's Office identified Kevin Douglas Limbaugh, 48, as the suspect in the officer's killing.

Kevin Douglas Limbaugh in a July 2018 booking photo.

Limbaugh left behind a letter, according to Davis police spokesman Lt. Paul Doroshov, who read the letter on camera to CNN affiliate KMAX

"The Davis police department has been hitting me with ultra sonic waves meant to keep dogs from barking. I notified the press, internal affairs, and even the FBI about it. I am highly sensitive to its affect [sic] on my inner ear," the letter reads. "I did my best to appease them, but they have continued for years and I can't live this way anymore."

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