SPOILER ALERT DISCLAIMER: This answer contains spoilers to the movie Looper.
Definitions and assumptions
In order to make the answer more readable, let's first declare that:
the one that lives in the present.
the one that came from 30 years later in the future to the present.
There are in fact two
First Younger is the one who shoots the
Older with the bag on his head (I will refer to this
Older as the
Second Younger is the one whom
First Younger, when he becomes
Second Older, meets when he goes back to the past, without the bag on his head, and meets the
There are some assumptions that are to be made in order to feel good with the suggested answer below:
- Knowledge is preserved through time when aging from
Older: in other words, whatever happens to a character, remains in his mind 30 years later.(1)
- Knowledge doesn't preserved through time backwards from
Younger: in other words, whatever happens to
Older in the future,
Younger will know nothing about it, unless
Older will tell him this.
- Experience changes through time: in other words, whatever changes in his life
Older may be affected by them, but as long as these changes are reversible, they exist as a possibility, and do not yet change
First Younger meets the
First Younger hasn't already lived his life 30 years in the future, and therefore, he has no real knowledge that his loop is going to be closed (although he does suspect this may happen sooner or later, since many of his fellow loopers had their loops closed lately). Then, he kills the
First Older and lives his life for the next 30 years, possessing the knowledge his loop is going to be closed. In 30 years from this incident, he becomes the
Second Older, who in comparison to the
First Older has an advantage of knowing how his life supposed to end(3), and he has the ability to do something against being killed.
Second Younger has no knowledge of the
First Younger having his loop already closed, so he is surprised to see his victim without a bag on his head.
Second Older is most likely shocked by the time travel, and it takes him few seconds to react, but it's a second less than it takes to the
Second Younger to react, and this way he is able to block the shot with the gold tied to his back, and to save his life.
Another important point to take notice of, is the flashback(4) that
First Younger sees before he shoots the
First Older in real time. This incident allows the
Second Older to improvise his escape from being killed by the
Second Older knows that
First Younger had this day-dream about missing his victim and going back to his apartment to retrieve the silver plates and to escape, and therefore
Second Older follows
Second Younger to his apartment after
Second Younger misses
Second Older and
Second Older escapes.
(2) The blurry thoughts of
Second Older when he sits in the bistro with
Second Younger versus the photo of
Second Older wife in his watch.
(3) We're getting into sort of a time paradox in here, since
Older supposed to have all the memories and the experience that
Younger has, and he supposed to know that his loops is going to be closed on the first time that
Older is sent back in time. A possible solution to this time paradox is to assume that an experience becomes a memory in the future only after it happened in the past, and there are no parallel possible time lines.
(4) Technically this is not a flashback, since he most likely day-dreams the whole scene while
First Younger waits for his victim to arrive from the future. We know that this was a day-dream/flashback only because we see that later he kills the
First Older, and later, in a similar way,
Second Younger shoots at the
Second Older, who already has the memory of this day-dream.