Complex sentence: He suffered a first heart attack whilst watching the film "Mondo Cane" at the Cannes Film Festival, 11 th May 1962; two more followed, the second of which killed him on 6 th June 1962.
Split into simpler sentences: He suffered a first heart attack whilst watching the film "Mondo Cane" at the Cannes Film Festival on 11 May 1962. Two more heart attacks followed, the second of which killed him on 6 June 1962.