City officials voted unanimously Tuesday to ask the U.S. attorney's office to investigate recent police shootings, including one of an unarmed man over the weekend, that have sparked four days of protests and a fiery clash between residents and officers.

Police stepped up patrols and some donned riot gears as hundreds demonstrated outside City Hall while many more packed the council chamber inside to discuss the shootings that have stoked anger over a spike in police shootings in the city. On the street, protesters tossed rocks and bottles at police and ignored warnings to disperse, forcing officers to form skirmish lines and fire pepper balls at the crowd.

At least two people were arrested, police Sgt. Bob Dunn said. At one point, police shut down a gas station when protesters were seen filling cans with gas, Dunn said.

The killing of Manuel Diaz, and another man Sunday, have taken the tally of shootings by police officers in this Orange County city to six so far this year, up from four a year before. Five of the incidents have been fatal.

On Tuesday, Diaz's family filed a civil rights lawsuit seeking $50 million in damages from the city of Anaheim and its police department, claiming he was shot while running away, said lawyer James Rumm.

Mayor Tom Tait said a description from court papers relayed to him by a reporter that Diaz had been shot in the leg and in the back of his head was "unsettling."

Theresa Smith, whose son was killed Dec. 11, 2009, by Anaheim police officers at a Walmart store, said she went by the scene of Saturday's shooting and was astounded by what she saw.

"There were pieces of brain on the ... darn grass, in front of all these children, in front of all these people," Smith said. "This traumatizes people and these people are angry."

The Anaheim police union issued a statement Tuesday defending the officers involved in the shootings and said both men killed were gang members who had criminal records.

The union also said that just before Diaz turned toward officers during Saturday's confrontation, he pulled an object from his waistband -- a common place where gang members hide guns.

"I believe that the independent investigations by the Orange County district attorney's office into both incidents will show no wrongdoing by these officers," said Kerry Condon, the police association's president.

Anaheim is a city of contrasts that ranges from upscale, hilltop homes to packed, gritty apartment complexes. The city 25 miles southeast of Los Angeles is known as home to the Angels baseball team, and above all, to world-famous Disneyland.

As California's Hispanic population has grown, so has the city's, hitting nearly 53 percent in 2010, census figures show.

Residents' concerns about the use of police force in the city aren't new. Last month, Anaheim decided to look into hiring an independent investigator to review shootings by police amid protests by relatives of those killed in officers' gunfire.

But Latino activists say that isn't enough and want federal officials to probe the Saturday shooting of an unarmed man in broad daylight who police say was a gang member.

Benny Diaz, state director of the League of United Latin American Citizens in California, said he wants a citizen review commission to keep tabs on the police department, officers to undergo sensitivity training and federal officials to investigate.

"People are saying, `you know what? We have to stop this,"' said Diaz, adding that residents' past requests for a probe of officer shootings have gone nowhere. "As an organization we are trying to find peace but there comes a point where you have to stand up strong."

Tait, who has called for state and federal agencies to investigate the shooting, urged the community to remain calm and said he wanted to address any concerns in the Latino community.

"If the Latino community is saying there is a rift, then there is rift, and we need to address that," he said.

Manuel Diaz's death sparked three nights of protests. On Saturday, angry demonstrators hurled rocks and bottles at officers who were securing the scene for investigators, and police responded by firing bean bags and pepper balls at the crowd.

On Sunday, protesters swarmed police headquarters during a morning news conference and later set fire to a trash bin and pushed it into the street outside the apartment complex. On Monday night, Diaz's mother was joined by the relatives of others killed in police shootings in a march near where her son was shot.

Police Chief John Welter said Saturday's incident occurred after two officers approached three men who were acting suspiciously in an alleyway before running away. One of the officers chased Diaz to the front of the apartment complex.

The chief would not say what exactly led the officer to shoot Diaz. But he failed to heed police orders to stop and threw something on the roof of the complex that contained what officers believe to be heroin, Welter said.

Both officers were placed on paid leave pending an investigation.

The second shooting occurred Sunday when anti-gang officers spotted a suspected gang member in a stolen sport utility vehicle. A brief pursuit ended when three people jumped from the vehicle and ran. One suspect fired at an officer and the officer fired back, killing the gunman, who was identified as 21-year-old Joel Mathew Acevedo, authorities said.

Both incidents were under investigation by the county's district attorney office, which asked witnesses to come forward with information or video footage of Saturday's shooting.

The FBI is conducting a review to determine whether a civil rights investigation is warranted, said agency spokeswoman Laura Eimiller.