there was an outstanding article about that (i think in the atlantic) discussing how various people reacted, and sometimes surprised themselves with their decisions on how they wanted to spend their “final” moments (a large amount of men went golfing with boxes of beer, people went to their favourite beauty spots, there was a guy that phoned his parents in a panic to hear that they’d argued about where they were going to go for the last minutes and through arguing had gone nowhere).
the ones that stuck with me were the amount of ex addicts who relapsed (mainly recovering alcoholics who though they were about to die and so had one last drink) and a guy who had dropped his children off at separate nurseries but then had no time to get to all of them and essentially had to pick which child he went back to.
like you say, i don’t know what they would have gone through but it would be fascinating to know, completely genuinely and off the cuff, how you would chose to spend your last moments. and what you would do with that knowledge if it turned out to be a false alarm.