SAN FRANCISCO (AP) — The family of a woman who was fatally stabbed at an Oakland train station is taking the first legal step toward suing the Northern California public transit system.

Attorney Robert Arns said his law firm delivered a legal claim Friday to the Bay Area Rapid Transit on behalf of the family of 18-year-old Nia Wilson.

She was killed in an unprovoked attack on her and her sister in an Oakland station on July 22. John Cowell, a 27-year-old parolee, has been charged with murder and attempted murder.

The family claims BART failed in its duty to ensure its customers are safe and that BART has failed to sufficiently address the problems of fare evasion and crime.

BART spokeswoman Alicia Trost says the system prioritizes safety for its riders.