Mentally Unstable Neighbour

I'm at my wit's end. My neighbor, a woman in her 30s, is mentally unstable and causing constant disturbances. She screams, yells, and throws tantrums throughout the day and night. Last year, she even threw a heavy object from her balcony, narrowly missing someone. To make matters worse, her erratic behavior has led to property damage within the building. After a year-long absence, she recently returned, leaving a tap open in her apartment, causing significant water damage to the floor below. The police have been called multiple times, but they seem helpless. Her family is aware of her condition but does nothing to help. The constant noise and unpredictable behavior have made it impossible to focus on work, study, or simply relax at home. I'm considering legal action, but I'm not sure where to start. Any advice would be greatly appreciated. Thanks