I spent a little time searching for Guilherme da Silva’s death date. I know that he arrived in San Francisco, California in 1918 with his wife and children. One of his sons was living in Oakland in 1930, but wasn’t living with his parents.
I searched Ancestry.com’s California Death Index, 1940-1997 using his immigrant name of William Silva. This did not return any matches so I expanded my search to all birth, marriage & death records on Ancestry.com. This also yielded no results. A more thorough search needs to occur trying other name variants.