The highest-ranking police official at the scene of a violent May 1 clash between officers and people at an immigration rally last week was demoted Monday and his second-in-charge was reassigned, Police Chief William Bratton said.

Deputy Chief Cayler "Lee" Carter Jr., commanding officer of Operations Central Bureau, was demoted to the rank of commander and assigned to his home. Cmdr. Louis Gray was moved to a post in the Office of Operations.

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Bratton announced the moves at a press conference along with Mayor Antonio Villaraigosa and the president of the city's civilian Police Commission, John Mack.

"I have to be comfortable with the leadership around me," Bratton said, but he noted that he could not state the specific reasons for the moves because they were personnel matters.

"This is a personnel decision, this is not a disciplinary action," Bratton said.

Police were videotaped using batons and firing rubber bullets at rally-goers and journalists gathered in MacArthur Park after an otherwise peaceful march for immigration reform. Bratton said a group of agitators threw rocks and bottles at officers wearing riot gear.

Neither Carter nor Gray returned messages left at their offices.

Carter has been in the department for more than three decades and was responsible for deployment of 1,700 officers serving more than 1 million residents in an area the size of Washington, D.C., according to the department's Web site.

Gray joined the force 39 years ago. A statement attributed to him on the Web site said he is a "strong supporter" of community policing.

"Forming partnerships with the community and solving problems together is the best way to combat crime and improve the quality of life for all persons who live and work in the City of Los Angeles," it said.

Los Angeles police leaders over the years have repeatedly faced intense public criticism for failing to take action after reports of police brutality.

Bratton is seeking a second five-year contract as chief. The local American Civil Liberties Union has stood by its endorsement of a second term for Bratton.

We all have responsibility and we're assuming that responsibility by ensuring that we get to the bottom of what happened here," Villaraigosa said.

Villaraigosa shortened a trade mission to Central America and returned to town Friday after criticism for being away during a swelling crisis.

The melee is the focus of four separate investigations.

The City Council Monday created a task force to monitor the internal police investigation into what happened.

"The health of our city depends even more now on our swift action, rigorous investigation and on our conduct of the people's business in broad daylight," said City Council President Eric Garcetti.