An 84-year-old woman was pushed to her death from a commuter train platform in Los Angeles' Little Tokyo by an apparent stranger, and investigators believe the victim did nothing to provoke the attack, authorities said Monday.

Betty Sugiyama was a retired bookstore worker who spent World War II in an internment camp for Japanese Americans. She was on the platform of the Metro Gold Line station with her sister Sunday morning when she was pushed on to empty tracks, Los Angeles County sheriff's Capt. Michael Parker said.

Sugiyama died hours later at a hospital.

Jackkqueline Pogue was arrested on suspicion of attempted murder and remained jailed Monday on $1 million bail. Authorities said they planned to seek a murder charge now that the victim is dead.

Investigators said the attack appeared to be unprovoked and there was no word on a motive.

Sugiyama's sister, Mary Sugiyama, said the two of them had planned a day of shopping in Long Beach, and despite both being in their 80s, they ran to catch the first of many trains they needed to take to get there.

"I didn't think we could make it," Mary Sugiyama told the Los Angeles Times. "But we decided to try."

Mary Sugiyama said she spotted a heavyset woman dressed in black and sitting alone, and as the sisters passed the woman stood up, shouted and shoved her sister onto the tracks, then sat back down without saying another word.

Mary Sugiyama said she could hear her sister's skull crack.

The two sisters grew up in Seattle and were in the same internment camp in Wyoming during the 1940s. Betty Sugiyama worked in several bookstores in Los Angeles' Little Tokyo and at one point ran her own bookstore, her sister said.

After retirement, she focused on other people's stores.

"She loved to shop," Mary Sugiyama said. "We made all the malls, I think."