According to police, the suspect was also shot by police at Burlington in the North Hollywood section of the San Fernando Valley.
Valentina Orellana Peralta was identified by the Los Angeles County coroner. The name of the suspect has not been released.
Witnesses reported to KCBS-TV, that a man started acting erratically and threatened to throw items from the top floor. He also attacked a woman using a bicycle lock just before noon, as the store was crowded by holiday shoppers.
Police said officers responded to a report that there had been an assault and shots were being fired. Police have yet to find a gun on the scene.
Police said that the suspect was shot and killed at the store. However, one of the bullets hit drywall behind him and killed the girl who was changing with her mother in a room.
The teenager was found dead by officers after they saw a hole in "a strong wall that you can't see beyond," LAPD Assistant Chief Dominic Choi stated.
He said that investigators did not immediately know if she was there before violence started or if she ran into the dressing room to hide.
"This tragic incident that resulted in the death of an innocent little girl is devastating and tragic for all involved," said Police Chief Michel Moore in a statement late Thursday evening. "I am deeply sorry for the loss in this young girl's lives and I know that there are no words to ease the pain felt by the family."
Moore promised a thorough, comprehensive and transparent investigation into the shooting. He also stated that a critical incident footage, which will include 911 calls and body cameras, would be released by Monday.
Investigators are trying to determine if the attack was targeted or random. Choi stated that they don't believe that the victim was related to the teenager.
Choi stated that police found a cable lock made of heavy metal near the suspect.
Attorney General Rob Bonta stated that the California Department of Justice was investigating this shooting.
According to news reports, a woman was seen with bloody eyes and was being taken to an ambulance.
Nicholas Prange, spokesperson for the Fire Department, stated that the victim was transported to the hospital with serious to moderate injuries. Choi stated that she sustained injuries to her head and arms, as well as her face.
This shooting recalls a confrontation that took place July 21, 2018, in which LAPD officers shot and killed a woman at a Trader Joe's Market. The officers engaged in a gunfight and shot their grandmother and his girlfriend, according to authorities. Police then pursued him outside the market.
Melyda Corado (27), assistant store manager was shot to death by a police bullet as she ran towards the store's entrance, having heard the car crash.
Authorities said that Gene Evin Atkins, the suspect, held employees and shoppers captive for three hours before finally surrendering to authorities.
Atkins pleaded not guilty for the murder.
Prosecutors determined that two officers of the police returned Atkins' gunfire and acted in good faith.