The scene sees Blunt's character Sara meeting and pointing a shotgun at Gordon-Levitt's Joseph Simmons.
The sci-fi action project follows Bruce Willis and Gordon-Levitt as the same character at different ages.
Looper is set in a future where time travel is possible but has been outlawed. 'Loopers' Blunt and Gordon-Levitt form part of a group who use time-bending technology in order to carry out assassination contracts.
Their targets are sent back in time several decades to meet them and be dispatched, but Gordon-Levitt finds himself face-to-face with his own future self (Bruce Willis).
A special featurette for the film from director Rian Johnson was released earlier this week.
Looper is released in the US and UK on September 28.
Watch a trailer for Looper below: