People protesting George Zimmerman's acquittal marched along Crenshaw Boulevard on Monday night, stomping on cars, chasing bystanders and storming a Wal-Mart.
Several protesters made their way into the Wal-Mart as guards scrambled to close security gates. A short while later, Los Angeles Police Department officers wearing helmets and carrying batons swarmed the store as others marched through the parking lot.
The LAPD declared a tactical alert about 9 p.m., which means that off-duty officers can be held on duty when their shifts end and may respond only to high-priority calls.
The LAPD arrested at least one person but vowed to take more into custody if the lawless actions continued.
"We want to support everyone's 1st Amendment right to protest, but we also want to ensure public safety and not allow people to commit violent acts," Cmdr. Andy Smith told The Times.
Police estimated that 80 to 150 people were engaged in lawless activity along Crenshaw as they jumped on top of vehicles and appeared to assault bystanders.
Some protesters ignited fireworks in the middle of Crenshaw.
Zimmerman, 29, was acquitted Saturday in Florida of second-degree murder and manslaughter in the 2012 shooting death of Trayvon Martin, 17.
The verdict has sparked protests across the county and led to arrests over the weekend in Oakland and Los Angeles.
On Monday evening, dozens of protesters gathered in Leimert Park for a vigil in support of Trayvon.
As James Brown music played, some danced and others wore shirts that read "Justice for Trayvon Martin." One man held up another shirt that showed Zimmerman with the words "Wanted Dead or Alive" with the last word crossed out.
The group broke up as marchers moved along Crenshaw Boulevard chanting "No justice, No Peace."
Los Angeles Police Department officers watched from a distance, while a police helicopter flew overhead.
In Oakland, protesters swarmed Interstate 880 near downtown and briefly shut down traffic in both directions Monday evening before they were cleared. Officials said arrests had been made as crowds moved to streets in the downtown area.
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