SAN FRANCISCO (KRON) — A 77-year-old woman died Friday after being attacked on Mother’s Day as she was getting off a MUNI bus in Chinatown.

The elderly woman, identified as Lin Leung, was hit in her head several times as she was getting off of the bus, causing her to fall to the ground. Her attacker is described only as an African-American woman.

Police believe a Good Samaritan, described only as a white male, helped the victim away from the bus and into a seated position on the sidewalk after she was struck in the head. But that person left the woman’s side before police arrived.

Through a post on Facebook, the victim’s granddaughter, Connie Ho, asked that the Good Samaritan or any other witnesses to come forward and get in touch with them or police. Sgt. Trevor Kelley with the San Francisco Police Department is investigating the case. He can be reached at trevor.kellysfgov.org or through the Anonymous Tip Line at (415) 575-4444 or by texting the tip to TIP411 with “SFPD” at the start of the message.

Investigators believe the incident happened between noon and 2:30 p.m. on May 10 in Chinatown, perhaps on Stockton Street.

Police said Tuesday that the assault was not connected to a robbery and that the motive for the assault remains under investigation.

The victim frequented the 2 Clement, 3 Jackson, 30 Stockton and the 45 Union/Stockton buses and she traveled often between the Chinatown and Japantown neighborhoods.