From left, Nancy Delgado, Pedro Antonio and his mother, Maria Perez, stand with others outside Hale Middle School in Woodland Hills, where helicopters drummed overhead and hundreds of officers searched for the gunman. (Anne Cusack / Los Angeles Times / January 19, 2011)

A second day of violence shook the Los Angeles Unified School District on Wednesday, with the shooting of a school police officer prompting officials to seal off a large swath of Woodland Hills and place about 9,000 students on lockdown for hours.

More than 350 officers swarmed through the West San Fernando Valley looking for the gunman, blocking people from entering or exiting a seven-square-mile area.

The shooting occurred just before noon adjacent to El Camino Real High School, where Officer Jeffrey Stenroos was patrolling. A gunman fired multiple shots at Stenroos, hitting him in the chest. A bulletproof vest prevented the bullet from penetrating his body, and his injuries are considered minor.

The shootings came a day after a student brought a gun onto the campus of Gardena High School. The gun accidentally went off in a classroom, police officials said, and two students were hit.

The incidents brought a collective shudder throughout the district and calls for better security in and around schools.

"We've never had two days like this in my 19 years here," said school board member Steve Zimmer. "Guns in and around school create a special kind of fear."

Melissa Warga had two children on lockdown most of the day, a 15-year-old girl at El Camino and an 8-year-old boy at Woodlake Elementary.

"There's something about what's happening now that has to stop," she said. "I'm so numb that my kids are enduring what they're enduring."

Incoming L.A. Unified Supt. John Deasy promised to launch an assessment of all high schools in the district to make sure they are following a district policy that requires random weapons searches to be conducted every day. He said Gardena High had violated district policy by not doing enough random weapons checks of students.

About four hours after Stenroos was shot, a 16-year-old Bell High School student was shot and wounded about half a block from the campus. In that case, a gunman in a black truck opened fire on the boy as he was walking home from school.

But the main focus of the LAPD remained in Woodland Hills. LAPD officials described the perimeter - which stretched from the 101 Freeway north to Oxnard Street - as one of the largest in recent memory. At the peak of the search, nine schools in the area were on lockdown.

The incident began when Stenroos, an eight-year veteran of the Los Angeles Unified police force, spotted the suspect on Manton Avenue near Burbank Boulevard involved in some kind of illegal activity, possibly breaking into cars, police said. He confronted the man, who pulled a gun and fired multiple rounds, hitting the officer once in the chest.

Los Angeles Police Chief Charlie Beck said the officer fell back and hit his head, but was able to stumble to his patrol car, where a civilian helped him radio for help.

The suspect, described as a white man in his 40s wearing blue jeans and a bomber jacket, fled and was last seen running east on Burbank Boulevard.

Stenroos was taken to Northridge Hospital Medical Center, where he was listed in stable condition.

"He's a lucky man," said Dr. Stephen Jones, medical director of emergency services. "The vest obviously saved his life."

Hundreds of officers from the LAPD, school police, the L.A. County Sheriff's Department and the California Highway Patrol swarmed the area around El Camino throughout the afternoon, cordoning off a seven-square-mile area. Firefighters called to the scene wore body armor. Helicopters drummed overhead.

Anxious parents gathered in the parking lot of Hale Middle School around 2 p.m., just beyond the perimeter.

Rachel Vred, who lives near El Camino High, was desperate to get home, where she had left her 8-year-old daughter with a nanny. She begged officers to let her in. "My daughter's sick," she told them. "Please, I need to get home."

All she knew was that "someone with a gun is running around the neighborhood."

Shelly Devito gazed through the chain-link fence with a strained look, helplessly waiting to get her two children at El Camino.

"Nobody's telling me anything, I can't get through. My kids are texting and calling me. They're stuck inside and not allowed to move. ... You think our kids are safe and they're not. It's that feeling. I don't know what to do with myself now."

She wiped her eyes. "I just want my kids."

Inside the schools, students said they had no access to water or restroom facilities. In at least one classroom, students relieved themselves in buckets placed in a closet.

Katie Testo, an 18-year-old senior at El Camino, said SWAT teams were combing the hallways of her school and students were still on lockdown in their classrooms late in the afternoon. "We're really anxious and really scared because we don't know what's going on," she said.

While some parents said they were worried about violence at schools, violent crime has actually been declining in L.A. County for some time. According to a Times analysis, neither Gardena High nor El Camino Real High is located in an area with high reports of violent crime. Since January 2007, two homicides have taken place within a mile of Gardena High. Over the last several months, few serious violent or property crimes have been reported close to El Camino.

The perimeter stranded thousands of people. Josh Morgan, 31, whose office is on Ventura Boulevard, said he and his colleagues tried to walk to lunch, but were turned back by police.

"We were able to leave the office, but made it about half a block down the street," Morgan said. He and his colleagues returned to work and ate potato chips and other snacks.

Ken Taylor, who owns a photo studio on Ostronic Drive, said he and his employees tried to leave the area after they heard about the shooting but were stopped by police searching for the gunman.

"The police stop every car ... they're opening their trunks," Taylor said. "They just want to make sure the suspect doesn't get out."

Taylor said police told him that if he left the area, he wouldn't be let back in. So he and his employees decided to return to the shop. "We locked our doors," he said.

Officials emphasized that the Woodland Hills incident was different from the one in Gardena. "This was not a schools shooting," said Los Angeles City Council President Eric Garcetti. "It was a shooting near a school."