"How To Go About Reimbursement On Destroyed Luggage"

"Traveling from Minneapolis was asked to check bag at gate. Upon arrival at salt lake international my bag never came at baggage claim. After talking with the delta agents for 30 minutes. When a man walked from the back holding a shredded suitcase with what was left of my belonging wrapped in sheet from my luggage. I am a traveling nurse and everything from my 400$ stethoscope meds scrubs multiple contacts and more were gone or damaged to a total loss. Any advice on how to go about it. They are saying I must provide receipts showing proof of purchase prior to the damage."
I genuinely wonder what it's like being a baggage handler.