Upstairs neighbors flooded my apartment and property management is ignoring me

My upstairs neighbor's washing machine hose burst last Tuesday while I was at work, and the water completely ruined my living room ceiling and hardwood floors. I reported it immediately to the building management, but they are dragging their feet and acting like it's not their problem to deal with. Meanwhile, there's a strong smell of mildew starting and parts of the drywall are literally caving in. I've sent three emails and called the front desk twice with no real response. What are my next steps here? Should I contact my renter's insurance first or get a lawyer involved?