There are two sentences:
Some people say that sentence 1 is ungrammatical (better say -- illogical), while sentence 2 is OK.
Why is it so? Why 那 makes such a big difference?
P.S. the examples are taken from :
Aspect, tense and mood : Context dependency and the marker LE in Mandarin Chinese Ljungqvist, Marita
p.s.s One guy told me that it is 一个人 conflicts with 可是没有杀死. That is, "one man" means that the killed person is unknown to the utterer but 可是没有杀死 says that the speaker somehow knows much more than the 一个人 phrasing suggests.