Outstanding detective work Karsten!
But I believe this was the wrong Konrad's death:
Peterson Konrad 51 y Apr 18 1930 #8780 Kings
The 1910, 1920, and 1925 Kings County New York censuses list a Konrad W. Peterson born ca 1879, married to Hulda, both born in Sweden.
His 1918 draft registration lists Konrad William Peterson born 12 November 1878, and records of Green-Wood Cemetery, Brooklyn list Konrad William Peterson buried 20 April 1930.
So, a coincidence, very possible with Brooklyn's large population.
If still alive and in USA 1917-18 there should also be a draft registration for Konrad S. P. born 1879, but I don't find one, any spelling.