The gunman who ambushed and killed a California cop left behind a letter ranting about how police were targeting him with “ultra sonic waves,” authorities said.

“The Davis Police department has been hitting me with ultra sonic waves meant to keep dogs from barking,” reads the one paragraph note, found in the home of Kevin Douglas Limbaugh, police said Saturday.

The typed letter continues: “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.”

The statement, which was discovered face up on the gunman’s bed, was signed: “Citizen Kevin Limbaugh,” Davis Police spokesman Lt. Paul Doroshov told the Sacramento Bee.

Investigators also found two semiautomatic handguns, a 9 mm and a .45 caliber, inside the home. It’s unclear who the firearms were registered to.

They match the descriptions of the guns Limbaugh used to kill 22-year-old “rising star” Davis Police officer Natalie Corona as she responded to a three-car crash Thursday, cops said.

The 48-year-old man had been ordered to surrender an AR-15 rifle in November after being convicted in a battery case stemming from an altercation where he punched a co-worker at the Cache Creek Casino Resort in the face.

After opening fire on Corona without warning Thursday night, Limbaugh shot in another direction, including toward a firefighter, Davis police Chief Darren Pytel said Friday.

The gunman had dropped his backpack and information inside led cops to his home one block away from the scene of the shooting, where they found him dead of a self-inflicted gunshot wound, Pytel said.

Hundreds of people attended a Saturday night vigil for the rookie cop, who had been on the force for less than a year.