Cara Jean Parks, also known as "Gigi", was shot at about 8:25 p.m. in the 2700 block of Hunter Street, police said.
Paramedics responded but Parks was pronounced dead at the scene from a single gunshot wound, police said.
Parks lived in a makeshift shelter about a half-mile from where she was shot, Liu said.
He said investigators have not determined where Parks was headed on her bicycle. No suspects have been identified in the case.
"We believe it's a targeted shooting," Liu said today. "We're still following up on leads right now to determine a motive and suspect information."
Anyone who may have witnessed the crime is urged to call Detective David Carson at (650) 853-5957, Detective Jeff Liu at (650) 853-3131, police dispatch at (650) 321-1112, or the Tip Line at (650) 853-8477.