Ancesrty has a database "Reports of Deaths of American Citizens Abroad, 1835-1974"
"Frank E Byrne died Jan 1 1961 4 p.m. Place of death: aboard the SS Exchequer enroute to NY from Barcelona Spain. B. Feb 5th 1896 last known address Chicago, ILcause: acute cardiac insufficiencyCertificate of death Municipal Court No 10 of Barcelona, signed Francisco Cerrillo Quilez, Judge (Book 66, Folio159 No.07)
Buried at sea Jan 8th 1861 SS Examiner enroute Barcelona Spain-Genova, Italy"
Disposition of effects: American Export Line
Discharge Book No. 042016 indicating his place and date of birth. Certif. of Death from local authorities kept at this Consulate's General's files. Mr Byrne's SSN is....
signed vice cousul of the USA James A. Parker"
This is from a scanned image of paperwork.
His death certificate should be available from the State Dept.