try to simplify the argument -
the second sentence states a condition -
Vicinity of a fire that large --> notice the fire.
the next sentence -
he went from his apartment to library --> he has to go past the Municipal building --> he was in the vicinity of the fire.
If we combine the above two sentences we get -
he went from his apartment to library --> he has to go past the Municipal building --> he was in the vicinity of the fire --> notice the fire.
the last part is the
...
the second sentence states a condition -
Vicinity of a fire that large --> notice the fire.
the next sentence -
he went from his apartment to library --> he has to go past the Municipal building --> he was in the vicinity of the fire.
If we combine the above two sentences we get -
he went from his apartment to library --> he has to go past the Municipal building --> he was in the vicinity of the fire --> notice the fire.
the last part is the
...






