What is discovered in The Hotel Zamenhof in the opening pages of the novel, The Yiddish Policemen’s Union?

In the novel's opening pages, Mayor Landsman is alerted to the discovery of a dead body, which is found in one of the rooms of the Zamenhof. The identity of the body is eventually revealed to be that of Mendel Shpilman, the son of crime boss Heskel Shpilman.