Children have been arrested in the US state of Washington for beating a 64-year-old disabled man to death.

A 12-year-old girl and two 13-year-old girls were charged with 'first' and 'second-degree murder' for beating Reggie Brown after chasing him down an alley on October 17.

The video shown at the sentencing hearing showed the children kicking 64-year-old Brown.

The autopsy report stated that Brown died of blunt head trauma.

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Brown's body was found in an alley at around 1 am on the night of October 17. One of the children claimed that they did not want to beat Brown but were forced to do so by a stranger who threatened them with a gun.