The California man who murdered a rookie police officer in an ambush and then killed himself as police closed in left a note indicating that he had delusions the police were targeting him with “ultrasonic waves,” the San Francisco Chronicle reported. Kevin Douglas Limbaugh, 48, was identified as the bike-riding gunman who opened fire on Davis Officer Natalie Corona as she responded to a car crash on Thursday. Limbaugh later shot himself in the head as officers surrounded his home. Police said he left a note face-up on his bed. “The Davis Police department has been hitting me with ultra sonic waves meant to keep dogs from barking,” read note. “I notified the press, internal affairs, and even the FBI about it. I am highly sensitive to its affect (sic) on my inner ear. I did my best to appease them, but they have continued for years and I can’t live this way anymore.” It was unclear if Limbaugh had been diagnosed with mental illness, but he had been ordered to surrender a semiautomatic assault rifle after a previous assault arrest.