The son of a California city police chief is expected to appear in court on Friday after he was arrested for beating an elderly Sikh man in an unprovoked attack that was caught on video.Tyrone McAllister, 18, has been charged, along with an unnamed 16-year-old, with second-degree robbery, harming an elderly adult and one other charge over the incident on Monday, which was recorded by a security camera on a nearby house.The video, posted online by officials in the city of Manteca in northern California, showed two men confronting the 71-year-old victim, who was wearing a turban and walking alone on a sidewalk. The pair kick him and knock him to the ground, before robbing him and spitting on him.Following McAllister's arrest on Wednesday, the police department of Union City, about an hour from Manteca, posted a letter on its Facebook page. In the letter, addressed to community members, Police Chief Darryl McAllister said the suspect in the case was his estranged son.Darryl McAllister said he and his wife had helped the Manteca police track down his son."Words can barely describe how embarrassed, dejected, and hurt my wife, daughters, and I feel right now. Violence and hatred is not what we have taught our children; intolerance for others is not even in our vocabulary, let alone our values," the police chief wrote.While neither Tyrone McAllister nor the teenager were charged with a hate crime, activists say the attack followed a number of beatings of US Sikhs over the past decade. Groups that track hate crimes say assailants have sometimes mistaken Sikhs for Muslims, who have also been targeted in hate crimes.McAllister is scheduled to appear in court at 1:30 p.m Californian time (2030 GMT). It was not immediately clear when the 16-year-old would appear in court or if McAllister had a lawyer.