Anonymous has backed victims of alleged police brutality in Anaheim, southern California, as violent street protests over the shooting of a young Latino man enter the fourth day.
The collective has called for "the citizens of the United States to rise up in unison" against what it says is aggressive police activity.
The hacktivists dumped the contact information online of Anaheim mayor Tom Tait and the city's police department in a campaign dubbed "Operation Anaheim".
"We want to inform the citizens of the world that the United States is setting the flames of revolution," the collective said in a video statement. "In Anaheim, police shot protesters and bystanders, including kids who did nothing wrong."
"The fate of America is in your hands," it continues. "Do you wish to be oppressed further, or do you wish to obtain freedom and peace?"
Violence erupted in Anaheim following the death of 25-year-old Manuel Diaz. He was reportedly shot twice by police in a residential neighbourhood, first in the leg and then in the head.
Local officers have already been accused by residents of running a "death squad", the Guardian reported.
When a second unnamed man was shot dead on Sunday, public anger grew stronger and residents took to the streets to allege police brutality.
Diaz's family filed a wrongful death suit against the city and called for peaceful demonstrations, appealing to the community for calm.
"Let's be peaceful," Diaz's mother, Genevieve Huizar, said at a news conference at the Orange County courthouse in nearby Santa Ana. "Peaceful demonstrations for everyone".
Latino leaders are angered over what they call "a history of brutality" against them. The city is divided between an eastern half, the Anaheim Hills, which is wealthy and conservative, and a western hal,f which is predominantly Latino, poor and economically depressed.
During a demonstration on Sunday, police lost control of a dog which bit mourners and protesters at the scene of Diaz's death.
Riot-clad officers have used batons, pepper balls and beanbag rounds to clamp down on protesters.
Solidarity marches are scheduled in cities across the country. The Occupy Los Angeles movement is planning a mass demonstration outside Anaheim police department on 29 July.