But the later image after the explosion shows the railing bent around the mail box in a way that is inconsistent with the explosive charge being in front of the railing where the bag is.
In looking at the second image I don’t agree that the railing was wrapped around the mail box. What I see is part of the railing is knocked to the side ( which could occur with the blast) while the portion of the railing directly behind the bag was most likely blasted away ( ie airborne or somewhere in the debris behind the blast) regardless I don’t see that the railing is wrapped merely knocked into the side of the mailbox.