EUGENE O'NEILL died on 1 December 1868 and was buried 2 December 1868 in Sacremento.
This information is according to a newspaper article dated march 1869 with information on EUGENE s death etc from Mr. MOONEY of the SAN FRANCISCO MONITOR.

I am unable to find any details of cause of death or where he is buried, or what he was doing in America.
He came from Melbourne AUSTRALIA c. 1867.
He had been an engineer on steamers.