DAVIS, Calif. (AP) — A gunman on a bicycle ambushed a rookie policewoman in Northern California, shooting her from the shadows, then reloaded and narrowly avoided wounding others before walking home and calmly watching the chaos he had caused, police said.

The man who gunned down Officer Natalie Corona in this small college town on Thursday night later killed himself in a house, but police still don't know the motive for the attack, Police Chief Darren Pytel said Friday.

The man's name was not released.

Corona, 22, died within minutes of arriving at the scene of a three-car accident. She was shot in the neck and then several other times as she lay on the ground.

"We're speculating that she never even saw him," Pytel said.

Christian Pascual, 25, was one of the drivers involved in the crash. He had handed Corona his license and she was returning it when he heard shots from close behind his right shoulder.

"The person was behind me," he told the Sacramento Bee.

"When I looked up and I saw the officer on the ground, he was already walking due west ... just shooting at what looked like random people to me," Pascual added.

The gunman sprayed bullets at a firetruck, a passing bus and a house, pausing to reload. Nobody else was wounded, although a firefighter at the scene was struck in a boot as he ran and a girl later found a bullet lodged in a textbook in her backpack, the police chief said.

Shaun Kingston, 39, saw the gunman shoot at the firetruck, "dump a clip and put another one in," and begin calmly walking away until Kingston, who followed at a distance, lost him in the crowd.

"He was just calm, cool and collected about it," he said. "It was pretty damn disturbing seeing someone do that and just walk away."

Police had had previous contact with the man, but nothing suspicious or indicating he had mental issues, the chief said. Last year, the man reported being a victim of a crime, he said.

The chief said that after the shooting, the killer "basically circled the block and went home."

At the rental home a few blocks away, he casually chatted and hung out with his roommate.

"He didn't show any sign that he was involved in the incident," Pytel said, and even went outside to watch as police from around the region began rushing to the shooting scene.

The gunman left behind a backpack that helped police track him to the house. The chief said as police began to surround it, he stepped outside wearing a bulletproof vest.

"He shouted some stuff, went back in and came back out with a firearm, then went back inside, pushed a couch in front of the door and officers heard a gunshot," Pytel said.

Police eventually sent a robotic camera in and found the shooter had shot himself in the head.

Police never fired, he said. They found two semi-automatic handguns in the home.

The shooting devastated the Davis Police Department, which has about 60 sworn officers and about 30 other employees. 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.

From the janitor to the police chief, Corona "just wanted to be everybody's friend, and was," the chief said.

Gov. Gavin Newsom issued a statement Friday saying the officer died "protecting her community from harm."

A candlelight vigil for the slain officer was scheduled Saturday night.

The attack occurred in a residential neighborhood up the street from a park that hosts a weekend farmer's market. Residents placed flowers at a growing memorial outside the police department Friday, where flags flew at half-staff.

Corona's colleagues, family and friends mourned a vibrant life that was cut short.

"She was the best of us," said Davis officer Mike Yu, after placing a "Blue Lives Matter" flag at the crime scene, about a mile from the police station.

As the eldest of four daughters, Corona grew up dreaming of becoming a law enforcement officer like her father, said her cousin, Emily Gomez, 26.

"I don't remember her talking about anything else than wanting to become an officer," said Gomez, who said her cousin was an athletic star in high school, excelling in volleyball, basketball and track. She grew up in a tight-knit family in the Northern California town of Arbuckle. The family had emigrated from Mexico a few generations ago and had become established members of their community.

Corona's father, Jose Merced Corona, spent 26 years as a Colusa County Sheriff's sergeant before retiring and getting elected to the county's Board of Supervisors last November. Her mother is a first-grade teacher, and two cousins are also in law enforcement, Gomez said.

Corona graduated from the Sacramento Police Academy last July and completed her training in December just before Christmas, officials said.

"She was very proud," her father told Fox40-TV, choking back tears as he spoke about how much she loved her job.

"She would come home, she would be beaming," her father said, his voice quivering. "She died doing what she wanted to do, what she loved."

He pinned the badge on his daughter at her swearing-in ceremony in August.

Corona was the second officer killed in California in the past two and a half weeks.

Cpl. Ronil Singh, 33, of the Newman Police Department was shot to death Dec. 26 after he stopped a suspected drunk driver.

Gustavo Arriaga Perez, also 33, was charged with the murder. Authorities said Perez Arriaga was in the country illegally and was preparing to flee to Mexico when he was arrested. That killing rekindled a debate over California's sanctuary law that limits cooperation by local officials with federal immigration authorities.

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Associated Press Writers Daisy Nguyen and Janie Har contributed to this report from San Francisco.