I am not sure where you live. Usually i have went to the airport and made a claim out with a airline agent.
There is usually one around the baggage pick up area. They corral up bags that passengers have not claimed. That is where i have taken my bag to have it inspected, and claim form filled out.
I have had rifle cases, similar to your also damaged by airlines. To have had the end sheared off on your case was the results of either being caught in a conveyer system or run over by a piece of moving equipment. a case like your with smooth sides and edges, means it had the ability to slide if it was on top of a load of luggage on a cart and probably was run over by a truck or tractor.
It should be noted that the airlines have a limit on what they will pay for damage to luggage. The amount you can claim is usually stated on their web site.
For sporting equipment, it has always been advisable to purchase additional coverage for your items being placed in the cargo hold, either through a private firm or with the airline when purchasing your ticket.