Here's a 1922 New York Times article that covers the reopening of the Seely Houk murder case. Apparently, County Detective J.N. Dunlop found evidence incriminating another man, not Rocco Racco. Here's a quote from the article: "County Detective J.N. Dunlap, who said he had discovered new evidence... swore out a warrant charging Jim Murdock with killing the warden." It looks like Rocco Racco did not deserve to be hanged, at least not for Seely Houk's murder.
Here's the link to the article: