A 10-year-old boy charged with murdering his father at their home in California was being exposed to his father's extreme neo-Nazi ideology of racism and violence at the time he allegedly turned a gun against him.

Evidence is mounting that Jeff Hall, 32, a white supremacist who led the National Socialist Movement in the south-west of the US, was involving his son in neo-Nazi activities before his death on 1 May.

A possible link between the group's violent messages and the shooting – an act exceptionally rare for a child as young as 10 – could be an important factor in the boy's trial.

Police were called to the Halls' home in Riverside, California, outside Los Angeles, shortly after 4am last Sunday, where they found Hall dead on a sofa. He had been shot with the family handgun.

Hall used his home as the headquarters of the NSM, one of America's largest and most influential neo-Nazi groups. A reporter for the New York Times witnessed Hall preaching race hatred at a meeting in front of the boy, his eldest of five children, a day before the shooting. Hall told the newspaper he was teaching the boy how to use a gun as well as night-vision gear and had given him a belt bearing Nazi SS insignia.

According to the Southern Poverty Law Centre, which monitors extreme right-wing groups, the NSM has a track record of recruiting very young children into its activities that surpasses that of any other organisation in the US. The party has created a children's wing called Viking Youth Corps, which is open to boys and girls with the proviso that they must be of European descent and the offspring of NSM members, or have their parents' consent.

The boy, unnamed by authorities due to his age, will be tried in a juvenile court. The local paper, the Press-Enterprise, described him as a "shaggy blond-haired, small, skinny, baby-faced boy". His defence lawyer indicated that he might pursue a plea of not guilty for reasons of insanity.

The boy's parents had been through a bitter divorce, and Hall and his former wife, Leticia Neal, had accused each other of abusing the child. The family has been monitored by social services since 2003.

The NSM was founded in 1994 and has grown in prominence over seven years. It now has about 400 members in 32 states. It advocates open race hatred, calling for the expatriation of all non-whites in America, and preaching antisemitism. Until 2007 its members wore Nazi uniforms with swastika armbands, but now wear black battle dress.

Hall, a plumber, was a prominent party member, involved in vigilantism along the Mexican border, organising patrols hunting illegal migrants. His house regularly attracted anti-racist protesters and he had put surveillance cameras on the property's exterior walls to keep guard on them. Hall's ashes are expected to be scattered along the Mexican border as a final political statement.

Jeff Schoep, NSM leader, described the dead man on the movement's website as a "dedicated father, his children were his life". He added: "See you in Valhalla!"