I think that a lot of "murders" that happen where a pistol shrimp is the assailant is similar to sharks at beaches most of the time (specially fish) that are killed by a pistol shrimp are (imo) mistakes by the shrimp itself...
Pistol Shrimp are a paranoid species and their also virtually blind...If there is 1 thing a pistol shrimp is forever doing, its refurbishing its home, always shifting moving things continuously, they rely a lot on their partner (goby) for general eye sight and even the goby isn't always safe from it's shrmp pal, the goby lets the shrimp know who it is all the time but consistently beating its fins/body against the shrimp in a consistent pattern thus the shrimp picks up on the pattern and understands its just his buddy goby, should the goby stop rubbing / beating it's fins on the shrimp. Then the shrimp will treat the goby as a threat and kill it, the goby is defenseless against a pistol shrimp.
Logically (in my view)
When the pistol is alone it percieves a lot of things as threats/food since it doesn't have its goby spotter to actually confirm/deny the threat, normally the goby would signal the shrimp whether this passing habitant is a threat/food or not and if it is a threat, the goby will dash into the cave and the pistol will come out to do combat.
All this relies more upon the goby and the decision it makes then relays to the pistol shrimp, without the goby well...yeah.