Using both blades at the same time - one in each hand - she slashed in a downward arc like in the movie "Psycho," sheriff's spokesman Steve Whitmore said.
"She was literally walking up and down the aisles slashing people," he said.
Police say Trawick, 34, was arrested when an off-duty sheriff's deputy pulled his gun and ordered the woman to the ground as screaming shoppers ran from the building.
A mother holding her baby was stabbed in the neck and was taken to the hospital, where she was in stable condition, Whitmore said. The baby was unhurt and all four victims are expected to survive.
One witness said she was shopping for a Mother's Day card when she heard someone screaming, "There is no witness protection program!" as chaos broke out in the store.
"I don't know what it means but she was yelling that repeatedly and at the top of her lungs," said Katy Winn, a freelance photographer from West Hollywood.
Winn said she dropped her basket and dashed across the store to the women's section, where she hid behind the clothing racks.
Los Angeles County Sheriff's Deputy Clay Grant Jr., said he was picking up paper towels and other items when people around him started running and screaming.
Grant, 26, grabbed his duty weapon, identified himself as a sheriff's deputy and ordered the woman to drop the knives, he said. She ran away and he followed her from aisle to aisle.
Grant was wearing a white T-shirt, camouflage shorts and running shoes so several shoppers mistook him for a gunman, adding to the sense of panic, sheriff's Sgt. Josh Mankini said. He followed Trawick from aisle to aisle, until she turned and waved the knives at him from above her head.
But he decided not to shoot because he didn't feel his life was in jeopardy, he said. For a second time, he ordered her to drop the knives and finally she complied.
"I was more concerned about the knife, more than what she was saying," Grant said. "Her facial expression was someone who was lost, confused, didn't know exactly where they were."
Trawick was arrested with the help of private security guards and held on $1 million bail on suspicion of attempted murder. Investigators were trying to determine whether the Antioch woman got the knives in the store.