After her shooting rampage, Yvonne Hiller called 911 and explained that she was fed up with what - in her mind - had been years of constant harassment from coworkers and neighbors.

She was plagued, mostly, by the idea that she was being sprayed with toxins and deer scent, certain that the smell was so strong in her immaculate Lawncrest home that no one would even park in front.

At her job in the sprawling Kraft Foods plant in Northeast Philadelphia, she clashed repeatedly with coworkers, who viewed her behavior with increasing alarm.

On Thursday night, near the end of her shift, Hiller's simmering anger boiled over once more, when she was waiting with a group of factory workers to take an annual hearing test, police sources said.

Three coworkers felt threatened enough to see the supervisor, who listened to both sides and decided to suspend Hiller - for the second time in recent years, sources said.

"She was known as the problem child," said Fred Capps, a 21-year employee and an acting shop steward. "It's always everybody's fault but Yvonne's."

Hiller, an employee for 15 years, who worked as a helper on the dough-mixing floor, was escorted off the property about 8:30. She got in her car and, moments later, returned to the gated back entrance to the plant, at Roosevelt Boulevard and Byberry Road.

She was armed with the .357 Magnum she legally bought in March and carried in her car. She pointed the gun at the two unarmed security guards and ordered them to open the gate.

Hiller, 43, the divorced mother of an adult son, returned to the third floor of the plant. She found the three coworkers in a break room with a fourth employee.

"The one she didn't have a problem with, she told, 'Get out,' and then she started firing," said Capt. James Clark, commander of the Homicide Unit.

LaTonya Brown, 36, a dough mixer, was shot in the head; Tanya Wilson, 47, also a dough mixer, was hit in the side. Both Philadelphia women died at the scene, Clark said.

The third victim, Bryant Dalton, 39, was hit in the neck. He was in critical condition Friday at Thomas Jefferson University Hospital.

During the initial confrontation, Capps said, Hiller was screaming at the three, leaving them shaken. She told Dalton, "I'm going to take you out," Capps said.

While they gave statements to the supervisor, Capps sat with them, Hiller storming into the room twice to interrupt. Then came Hiller's turn.

"It wasn't a statement," Capps said. "It was a rant. About 9/11, about Muslims, about how people have been spraying her with chemicals for years, spraying her car, her house."

He recalled her saying, "You don't know what these chemicals are doing to me."

Brown's mother, Terral, said she had spoken to her daughter Thursday night after the dispute with Hiller for about a half-hour. Her daughter said, "There have been multiple complaints about this woman."

"My daughter told me that she was scared because of Hiller, and that this girl was crazy," Terral Brown said. " 'I don't feel safe today, Mom,' she said. 'I'm scared.' "

Her daughter, who had four children, ended the call abruptly about 7:30, promising to call back.

"That was the last thing I heard from her," Terral Brown said.

After shooting her coworkers, Hiller sought out and fired a shot at her supervisor, police said. She also fired at another employee - described as either a mechanic or maintenance man - who was following her through the building, warning employees to flee and talking to police on his cell phone.

Hiller missed both targets.

Police officials praised the mechanic's cool head and bravery, saying he saved countless lives. They did not give his name, and his union president also refused to identify him. Capps knew only his first name, Dave.

"Dave's the hero," he said.

Hiller made her way to the second floor and barricaded herself in a cinderblock laboratory - the quality control area - in the middle of a huge factory space.

The first responding officers, from the Seventh and Eighth Districts, were directed to the laboratory by Dave the mechanic.

"We would have had to search a very large and complex facility," said Chief Inspector Joseph Sullivan. "He saved lives, saved time."

Hiller may have fired a shot through the wall at those first officers, who backed off as a SWAT team arrived, Sullivan said.

Seven employees also were in the lab, hiding in a side room that Sullivan likened to a closet. "They had the presence of mind to turn off the lights and crouch down," he said. None was harmed.

Hiller, meanwhile, made several calls, including to her former father-in-law and mother-in-law, sources said. Then she called 911, and a supervisor, Cpl. Janice Leader, got on the line.

Hiller sounded "exhausted, like a weight had been lifted off her," Leader said.

"She told me to say goodbye to her son," she recounted. "I said, 'You'll see your son tomorrow.' . . . I just didn't want her to hurt anyone else."

After about 40 minutes, Hiller said she saw the lab door opening. Leader, who had been communicating with the SWAT team, knew the officers were entering.

She told Hiller to put the gun on the floor and put her hands on her head - and Hiller complied. She was arrested about 9:30.

The gun was empty. Although Hiller had more ammunition, she had not reloaded.

Hiller gave a statement to homicide detectives reiterating that she was being sprayed with toxins and saying she had proof that her home was contaminated, sources said.

She also told detectives that she had been treated for mental illness, sources said. She told Leader that she took medication, though she did not specify what kind.

Hiller said she was certain she was going to be fired, and showed little emotion other than frustration, sources said.

She has been charged with two counts of murder, attempted murder, aggravated assault, and other offenses.

The Kraft Foods plant, for many years known as the Nabisco factory, was closed Friday "until further notice," the company said. Kraft makes Ritz crackers, Lorna Doone cookies, and other baked goods there.

Employees who worked earlier in the week will be paid their full 40 hours, the company said.

"This is a heartbreaking time for the Kraft Foods family," said Joyce Hodel of Kraft Foods corporate affairs.

In a statement, she described Hiller as becoming agitated and using profanity Thursday night, and said Hiller's company ID had been confiscated when she was escorted off the property.

Hodel acknowledged that "from time to time, [Hiller] had run-ins with others. However, we don't believe she had a history of violent behavior."

Although Hiller did not have a criminal history, Clark said, she had at least one previous physical confrontation with an employee.

Hodel said she could not discuss Hiller's employee history further due to privacy concerns.

"The safety of our employees is our first priority," she said. "Our immediate goal is to provide support for our employees, to fully understand what happened, and take appropriate action to prevent it from occurring again."

Brown's mother blamed the company.

"What kind of security is this," she asked, "and why was this woman still at work after all these complaints?"

Nearly 500 people work at the plant. About 100 employees were there when the shooting occurred.

Union leader John Lazar praised the company, the working conditions, and the labor relations. "It's a good, blue-collar union job," he said, "and they are rare right now."

He declined to discuss employee concerns about Hiller or the company's response.

The rampage was the deadliest workplace killing in Philadelphia since February 2007, when a disgruntled investor armed with two handguns killed three businessmen and wounded a fourth in a conference room at the Naval Business Center in South Philadelphia. The gunman later killed himself.