The lawyer for Hollywood filmmaker Peter Rodger said that the "family believes the child was the perpetrator".
Alan Shifman said the son had Asperger's syndrome, had trouble making friends and had been receiving professional help.
Mr Shifman added that the family had contacted police about "recent posts on YouTube" by Elliot "regarding suicide and the killing of people". The family is "devastated" and co-operating with police, he said.
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The plans had been in development since 2014, but would help underline Britain as a "global player" following the Brexit result.
The number of calls about children suffering or witnessing emotional abuse or physical violence in the home has surged in recent years.
The curtain will come down on the show for the final time at the Piccadilly Theatre in March next year, before embarking on a UK tour.