Baggage stolen at airline- inside job?

So those tags that say you have a gun in your bag are doing more harm than good. My mother-in-law was flying from AK to Seatac with a handgun checked in her luggage. Her bag went missing from the baggage claim. Later after reviewing security tapes they found a guy who had taken two bags, both with handguns. The bags had been diverted to a different baggage claim and they saw the crook on his cell, most likely talking to a ramper. Anyway, the cops are on it, however- what legal avenues would you persue if this happened to you? They said this has happened before to other passengers.