Image copyright Manteca Police Department Image caption Tyrone McAllister, 18, is the estranged son of the police chief

A Northern California police chief has said he was "disgusted" to hear his estranged son was arrested in an attack on a 71-year-old Sikh grandfather.

Footage of the attack showed Sahib Singh Natt walking on Monday when he was confronted by two men. One of them began kicking him as he fell down.

Union City Police Chief Darryl McAllister later revealed that his 18-year-old son was a suspect.

Police say they are investigating it as an attempted robbery, not a hate crime.

"Words can barely describe how embarrassed, dejected, and hurt my wife, daughters, and I feel right now," Mr McAllister wrote lengthy Facebook post after learning of his son's alleged involvement.

"Violence and hatred is not what we have taught our children; intolerance for others is not even in our vocabulary, let alone our values."

Media playback is unsupported on your device Media caption Footage showed Sahib Singh Natt being confronted by two men before being knocked down and kicked

The police chief's son, Tyrone McAllister, was taken into custody on Wednesday and has not yet filed a plea.

He faces felony charges for allegedly attacking Mr Natt as he walked by a park in nearby Manteca, California,

Chief McAllister is not handling the case, but said he helped Manteca police locate his son, who has been estranged from him for several months.

Surveillance video footage shows two men wearing hooded sweatshirts approach Mr Natt, who does not speak English.

One of the men then begins to kick Mr Natt, who falls on to the pavement.

The men start to walk away, but the suspect who attacked him returns to kick him three more times while he remains on the ground.

The man spits on Mr Natt and runs away as the elderly man lies unmoving on the street.

Police told local media one of the men may have brandished a firearm in the air as they left.

"The victim suffered only minor physical injuries, but as you can imagine, the greater Sikh community is devastated", Chief McAllister wrote.

"Despite having the desire any parent would have in wanting to protect their child, my oath is (and always will be) to the law," he added.

"My stomach has been churning from the moment I learned this news."

Mr Natt's family told KGO-TV that the grandfather made his way home, injured. He has since been treated and released from hospital.

"Everybody's scared, you know, me, everybody," his son-in-law, Maneet Singh Virk said.

Manteca city police said the incident is likely an attempted robbery and that "at this time, there are no indications that this assault was a hate crime".

Image copyright Getty Images Image caption Sikhs in New York arranged a Turban Day in Times Square last year to educate people about the Sikh religion

Prabhjot Singh of The Sikh Coalition civil rights group told KGO-TV: "It doesn't matter that the assailant was the son of a police chief. It could have been anyone."

Sikhism hails from the Indian subcontinent, and observant Sikhs wear turbans. Members of the community have been attacked in the past by assailants mistaking them for Muslims.

The assault on Mr Natt is the second in California in recent weeks.

Earlier this month, Surjit Singh Malhi, 50, was beaten by two men as he put up campaign signs for local Republican candidates in Stanislaus County.

The men also vandalised Mr Malhi's vehicle, spray-painting the words "Go back to your country" with a white supremacist symbol, CBS Sacramento reported.