LOS ANGELES - Police throughout California arrested hundreds of people who refused to heed curfews, chasing some down after they smashed into stores following a weekend of violence that accompanied rage over George Floyd's death at the hands of Minneapolis police.

Monday's violence and thefts were not on the scale of the weekend, when blocks of stores were devastated, police cars torched and many officers injured.

Most of Monday's protests were smaller, although an estimated 15,000 people gathered in Oakland and about 5,000 demonstrated in Riverside, east of Los Angeles.

In Sacramento, where two-thirds of the downtown businesses were damaged over the weekend, 500 National Guard troops were deployed and the city declared a Monday night curfew.

Most demonstrations were peaceful and there was sympathy expressed by law enforcement. Riverside County Sheriff Chad Bianco took a knee at the invitation of demonstrators.

"We support and will protect those who wish to demonstrate peacefully," Los Angeles U.S. Attorney Nick Hanna said in a statement that announced the FBI will help identify those who commit serious crimes.

San Diego Police Chief David Nisleit said Floyd's death prompted him to revisit department policy and stop using a controversial neck restraint method. Floyd, who was black, was handcuffed and on the ground pleading for air as a white police officer pressed a knee on his neck for several minutes.

Los Angeles Police Chief Michel Moore criticized looters as capitalizing on the death of Floyd and said "his death is on their hands." Moore quickly said he regretted that characterization but added he was not apologizing to those committing violence and destroying livelihoods.

"Looting is wrong, but it is not the equivalent of murder and I did not mean to equate the two," Moore said later. "Let me be clear: the police officers involved were responsible for the death of Mr. George Floyd."

Most of Monday's demonstrations ended when curfews took effect. But remaining crowds tossed fireworks and bottles in several cities, and authorities responded with tear gas and rubber bullets.

Police who had been overwhelmed during the weekend were reinforced by 4,500 National Guard troops.

"Don't be dumb," Los Angeles Mayor Eric Garcetti warned before the night's curfew went into effect.

Even so, scattered attacks on stores threatened to overshadow the message of protesters. Televised images showed attacks on stores in Van Nuys and Hollywood. Police said some people carried hammers.

At one point, a handful of protesters stopped would-be thieves from entering a Walgreens on Sunset Boulevard.

Many of the trashed businesses had only recently reopened following weeks closures because of the coronavirus. Volunteers turned out to help merchants clean up broken glass, board storefronts, and scrub away graffiti.

Alex Rose clutched a garbage-picker as he joined others cleaning up downtown Sacramento.

"There's a very clear distinction between protesters and the looters," said Rose, who protested during the day Sunday. "I went home last night, and that's when the criminals came out."

Some leaders blamed outsiders for the violence.

Oakland's acting police chief said organized thieves traveled more than 100 miles (160 kilometers) from other cities.

"Fifteen, 20, 30 cars at a time, hitting as you've seen different shopping malls, different areas," Chief Susan Manheimer said.

San Francisco Police Chief Bill Scott said some people "came to this city with crowbars, bolt cutter, tools that were designed specifically to get into businesses, to take property and loot."