Possible Clues:

• Death sentence widely publicised?
• 'I'll believe that when I see it!'
• "Et tu, Brute?," e.g
• Star's awful moods could produce ironic comment
• Overly-optimistic statement, passing comment?
• Et tu Brute? How wrong I was!
• Wit's formula, so sad, spouted with one passing away?
• Something memorable said on the way out?
• Precalamity pronouncement