Nina Susu, 20, of Sacramento, California, was fatally shot on September 8, 2001, at the city corporation yard. She had worked as a security guard for Burns International Security and had recently ended a relationship with a colleague, Joseph Ferguson. After the breakup Ferguson vandalized Nina’s car with an ax and was suspended from the job.

Family and authorities said Ferguson had threatened Nina and others; those threats were reported to the FBI and local police but, according to accounts, no immediate action was taken because he had no criminal record. On September 8 Ferguson began a killing spree that included Nina among five people he killed and two he wounded over two days. He recorded a video outlining plans to target former co-workers and, after a high-speed chase and shootout with police on September 10, Ferguson died by suicide.

What additional details about Nina’s life or the warnings before the attacks might help explain how such threats weren’t stopped?