The gunman who fatally shot a rookie Davis, California, police officer Thursday as she investigated a traffic accident had obtained two handguns despite a criminal protection order that barred him from possessing firearms, reports the Sacramento Bee.

The weapons weren't registered to 48-year-old Kevin Douglas Limbaugh, according to the paper.

Investigators in the college town near Sacramento say Limbaugh approached 22-year-old officer Natalie Corona on a bicycle and ambushed her, shooting her from the shadows, then reloaded and narrowly avoided wounding others before walking to his home a few blocks away. Police said Limbaugh left behind a backpack that helped police track him to the house.

Davis Police Department officials said 22-year-old Officer Natalie Corona was shot after responding to a three-car traffic accident at about 6:45 p.m. CBS Sacramento

As police began to surround it, he stepped outside wearing a bulletproof vest and brandished a gun, then went back inside the home and fatally shot himself.

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Detectives subsequently found the two semi-automatic handguns, as well as a note he left on his pillow that blamed the police department for "hitting me with ultra sonic waves meant to keep dogs from barking."

Limbaugh was charged and convicted in a battery case in Yolo County last September after he allegedly sucker-punched a co-worker at the Cache Creek Casino Resort, according to court records cited by the Bee.

The criminal protective order reportedly required that Limbaugh "must not own, possess, buy or try to buy, receive, or otherwise obtain a firearm or ammunition." The order, which was to be in place for three years, also required him to stay away from the victim and to turn over any firearms of which he was already in possession within 24 hours. The paper reports Limbaugh turned over a black .223-caliber AR-15 Bushmaster rifle to police in November.

Davis Police Lt. Paul Doroshov told the paper Monday investigators still don't know how Limbaugh obtained the two unregistered handguns.

Kevin Limbaugh CBS San Francisco

"It's still unknown," Doroshov said. "His having these [weapons] is illegal with a standing order, but it is possible to have unregistered weapons. The investigation is going to shake out where these weapons were from."

Corona was the first officer in the department to die in the line of duty since 1959. She had only been patrolling solo for about two weeks, the chief said.

Davis Police Chief Darren Pytel told reporters Corona was "a rising star in the department ... I've heard her described by our officers tonight as our daughter, our friend, and just a sister that we all wanted. This is just an absolutely devastating loss to the police department."

Corona followed in the footsteps of her father, Merced Corona, a former deputy with the Colusa County Sheriff's Department.

Merced Corona told CBS San Francisco he was proud of his daughter and was honored to pin on her police badge when she graduated from the police academy in July.

"She died doing what she wanted to do, which was being in law enforcement," Merced Corona told the station.