Both assaults involved several juvenile suspects, but police have not directly linked the two cases.
On Jan. 24 at about 6:20 p.m., five boys assaulted 83-year-old Huan Chen, after he left a bus stop at Third Street and Oakdale Avenue, police said.
Chen, of San Francisco, was taken to San Francisco General Hospital with a head injury and died on March 19, according to police.
The medical examiner's office is still investigating whether the injuries from the assault directly caused Chen's death, and has not yet ruled the case a homicide.
On Monday, five boys attacked a 57-year-old woman on a Muni light-rail vehicle platform at Third Street and Oakdale Avenue at about 7:30 p.m., according to police.
One of the suspects threw the woman from the platform onto the tracks and continued to assault her, police said. She was treated for injuries that were not considered life threatening.
The attack was caught on Muni surveillance video, and police Wednesday arrested a 15-year-old San Francisco boy believed to have thrown the woman onto the tracks and assaulted her. The boy, who has not been named, was charged with assault and remains in custody.
The motives for the attacks are still being investigated, but neither victim was robbed, police said.
Anyone with information about either case, or who may have been the victim of any similar incidents, is asked to contact police.