San Francisco ? Viral videos of riot police repeatedly pepper spraying a row of seated, nonviolent Occupy Wall Street protesters at a California university has sparked outrage, an investigation and calls for the college chancellor’s resignation.

It has also set off a debate about whether the officers were justified and how far they can go to disperse peaceful demonstrators.

While many students, lawmakers and even the university’s chancellor saw the officers’ actions as excessive, some experts on police tactics say depending on the circumstances, pepper spray can be a better crowd control measure than dragging protesters away or swinging at them with truncheons.

“Between verbalized commands and knock-down, drag-out fights, there’s quite a bit of wiggle room,” said David Klinger, a former Los Angeles Police Department officer and instructor at the University of Missouri-St. Louis. “When you’ve got a bunch of people who are clearly noncompliant, locking arms, it doesn’t look good (on camera).”

Soon after the spraying on Friday at University of California, Davis, video recordings spread across the Internet. The footage of an officer casually spreading an orange cloud over protesters while spectators screamed in horror joined other much-discussed pepper-spray incidents, such as the 84-year-old activist hit in the face in Seattle and a Portland, Ore., woman who was sprayed in the mouth.

The university announced Monday that it has placed the police chief and two officers on administrative leave to restore trust.

Still, nearly 2,000 students and residents gathered Monday at the main quad to hear speeches and chant slogans against police and university officials. Students who were pepper-sprayed opened the protest, saying they now feel unsafe on campus.

“We were just kids sitting down in a circle singing,” said mechanical engineering student David Buscho, 22, of San Rafael, Calif. “It felt like hot glass. … I was paralyzed with fear.”

Pepper spray is an inflammatory agent that derives its active ingredient from chili peppers. When the spray is deployed, it causes nearly instant inflammation, resulting in dilation of the capillaries in the eyes, paralysis of the larynx and a burning sensation on the skin.

Students used pink and purple chalk to scrawl messages of peace such as “One Love” on sidewalks.

Buscho said students were yelling at police Friday that they were peacefully protesting. One of the helmeted officers began pointing a spray can directly at protesters’ faces, he said.

“I had my arms around my girlfriend. I just kissed her on the forehead, and then he sprayed us,” he said. “Immediately, we were blinded. … He just sprayed us again and again, and we were completely powerless to do anything.”

The protest Friday was held in support of the overall Occupy Wall Street movement and in solidarity with protesters at the University of California, Berkeley who were struck by police with batons on Nov. 9. Nine UC Davis students hit by pepper spray were treated, two were taken to hospitals and later released, university officials said. Ten people were arrested.