He is behind the gun

This subtle malaphor is a mash up of “behind the 8 ball” (in trouble) and “under the gun” (under pressure).  Both idioms are very similar in meaning.  The context was facing a deadline, so the speaker probably meant under the gun.  The words behind and under are similar in indicating location, which I think adds to the mix up.  Many thanks to Senior Malaphor Hunter Mike Kovacs (note the title in caps).