Recourse with Apartment Owner for Mold Issue

My son who lives in California has encountered a mold problem in a closet caused by a leaking sprinkler valve, The apartment complex had recently replaced all the sprinkler heads, but forgot this one. The room in their apartment where closet is located has been closed off due to the mold issue. Is the apartment complex responsible for the cost of replacing the belongings lost due to the mold issue?