NBC News – A day after violent protests over the acquittal of George Zimmerman in the death of Trayvon Martin, city leaders and activists urged peace even as a leading civil rights activist said demonstrations will continue all summer – starting with vigils in 100 cities on Saturday.

“We don’t want anyone hurt. We don’t want any cars broken into, and we don’t want any damages to business,” Eddie Jones of the Los Angeles Civil Rights Association  told NBCLosAngeles.com.

L.A. Mayor Eric Garcetti and LAPD Chief Charlie Beck called for calm in a Tuesday afternoon news conference after a second night of unrest in the city in which 14 people were arrested, most for failing to disperse after people clashed with police, attacked a news crew and threw rocks.

Beck said lawbreakers wouldn’t be tolerated. “You come here again tonight, you will go to jail,” he said.

“We are calling on people to practice peace,” Garcetti said, “to not let the dialogue sparked by Martin’s death be silenced by any violence.”

The warnings and pleas appeared to have been effective. A peaceful crowd of about 200 marched along downtown streets Tuesday evening, blocking traffic, the Los Angeles Times reported on its website. But the group had dispersed by 8:30 p.m. (11:30 p.m. ET), the Times reported.

City leaders in Oakland, Calif., also called for protesters to be peaceful after a Monday night demonstration sank into chaos. Nine people were arrested and several businesses were vandalized. A businessman dining in a restaurant that was vandalized said a protester assaulted a waiter.

Interim Oakland Police Chief Sean Whent said Tuesday that his department was caught off guard and added no staffing ahead of the protests that erupted Saturday because he was unaware that the Zimmerman jury was deliberating on the weekend, NBCBayArea.com reported.

Meanwhile, the Rev. Al Sharpton announced vigils across the country that will be followed by marches in Tallahassee, Fla., and Washington, D.C.

“Florida will be the battleground of a new civil rights movement,” Sharpton said during a news conference with other clergy outside the Justice Department headquarters.

“We are not having a two- or three-day anger fit,” said Sharpton,who is president of the National Action Network and also hosts a show on MSNBC. “This is a movement for social justice.”

Sharpton said the nationwide action has two goals: urging the Justice Department to move forward with a civil-rights probe of Zimmerman and repealing “Stand Your Ground” self-defense laws that some say made it difficult to win a conviction in the case.

Rallies and vigils have been held by Martin supporters in major cities since a Florida jury found Zimmerman not guilty on Saturday night. They have been mostly peaceful, though 14 people were arrested Monday night in Los Angeles after a gathering descended into chaos with some people throwing rocks, attacking people and clashing with police, NBCLosAngeles.com reported.

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