Limbaugh was ordered last fall to surrender a semiautomatic rifle after he was convicted in a battery case.
The note left by Kevin Douglas Limbaugh of Davis, Calif., was released after Davis police identified the 48-year-old as the man who fatally shot Corona during the officer's response to a vehicle collision Thursday night.
Corona was shot multiple times, Davis police Chief Darren Pytel said.
The note found in his home reads in part, "the Davis police are hitting me with ultrasonic waves meant to keep dogs from barking".
48-year-old Limbaugh is the man police say killed officer Natalie Corona. Her father, a 26-year veteran of the Colusa County (California) Sheriff's Department, told NBC Bay Area that she rarely discussed anything else.
The 22-year-old completed field training before Christmas, Pytel said, and soon the department's "rising star" was out on her own.
After hearing a single gunshot inside, the officers sent a robot where Limbaugh was found to have fatally shot himself in the head.
The gunman left behind a backpack that helped police track him to the house.
Corona realized her dream in August upon graduating from the police academy.
Doroshov said Limbaugh did not make any formal complaints with the Police Department.
No one else was injured in the attack besides Corona, who died at the UC Davis Medical Center in Sacramento.
"I'd really like to see as many people as possible from the community attend", Pytel said during Saturday's vigil at Davis' Central Park, which was attended by at least 1,000 people. "But just seeing you all here does make a difference". At 10 pm Thursday night they arrived at the home.
Doroshov said investigators found two semiautomatic handguns at Limbaugh's apartment and were trying to determine how he obtained them.
The suspect went on to say in his note, "I notified the press, Internal Affairs, and even the FBI" and that "he can't live this way anymore". There, the Sacramento Bee reports, several members of the Davis police force shared anecdotes illustrating Corona's commitment to helping others.
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