Firing frame position not updated when the player dies
From DoomWiki.org
The position of firing frame sprites is not updated if the player dies while in the course of firing a shot from a weapon.
When the player is killed, the weapon sprite is gradually lowered until it is off-screen and out of sight. When the player shoots, the firing frame is drawn over the current weapon frame with relative positioning, so that the weapon appears as if it is shooting. When the player dies, however, this position is not updated, so the firing frame remains in place on the screen until its current frame is complete, and then abruptly disappears. This can generally be seen only for a very short time, often a fraction of a second, as most weapon frames change quickly to create a believable perception of motion. The engine does not draw the next frame in the animation, as it "notices" that the player is now dead.