Marsh's family said the victim and her sister know the shooter.
"She was my angel, she jumped in front of a bullet for me," said Lakeva Morganfield, Marsh's sister.
Morganfield was walking with her sister when she was shot and killed in the 800-block of Weller in the South Austin neighborhood around 9 p.m. The two were headed to their grandmother's house when a woman with whom they said they were in longtime dispute approached them with a gun.
"The girl was waving the gun at both of us," said Morganfield. "I'm telling her to move. (She's) telling me to move. And a shot went off..."
Morganfield said her sister collapsed and died almost immediately. The 15-year-old was a sophomore at Orr High School. She was interested in studying graphic design, according to her mother.
"She was involved in everything at school. She was talking about going to college. That's a waste," said Kimberly Marsh, victim's mother.
Marsh's family is now focusing on finding the woman they believe killed her.
"If the police don't find this girl, there's no justice," said Morganfield.
"They know who they're looking for. She should turn herself in. It should be on her conscience," said Marsh.
Marsh was one of three Chicago Public Schools students killed by gunfire over the weekend.
"We need to continue to make our children safe and lobby gun laws. It makes no sense to have eight school children shot over a weekend and three of them dead," said Arne Duncan, CPS president.