KNOXVILLE, Tenn. (AP) — Almost a year before he was accused in a deadly shooting outside a hospital, Abdo Ibssa violently attacked a stranger he suspected was saying something bad about him in a store, according to a lawyer who filed a lawsuit in the case.

On Monday, Ibssa fired a volley of bullets that killed one hospital worker and wounded two others because, police say, he thought his doctor had implanted a tracking chip in him during an appendectomy in 2001. Ibssa then shot himself, dying at the hospital entrance.

Police say Ibssa, who had been committed to mental treatment by his family earlier this year, appeared to have quit taking his medication for schizophrenia.

His erratic behavior dates at least to May 2009, when the store confrontation occurred. Jalal Boudarga sued Ibssa for $300,000 in January. His attorney, Jerry Martin, said Ibssa blocked Boudarga in the store parking lot with his car and then began yelling at him. Ibssa shoved Boudarga violently against his vehicle, causing him to hit the ground and break his leg.

Martin said Boudarga’s leg was broken so badly that he had to have surgery, six screws and a metal plate placed in his bones.

“I guess if Mr. Ibssa imagined that a doctor had put a computer chip in him, then it’s not that far of a jump for him to imagine my client saying something about him,” Martin said.

The lawsuit provides some of the few details about Ibssa’s life in Knoxville. The Ethiopian immigrant had become a naturalized U.S. citizen and moved to the Tennessee city.

Neighbors declined to talk to The Associated Press. A store operated by Ibssa was closed, and calls to possible relatives were not returned.

Ibssa entered a medical tower near Parkwest Medical Center before the attack and asked for the doctor who performed the appendectomy, Knoxville Police Chief Sterling Owen IV said. Unable to find the doctor, Ibssa went to another area where patients are discharged and opened fire on the women as they walked out of the building.

Ibssa, who police believe had been skipping doses of medication for psychotic behavior, killed himself to end the shooting, which occurred a day before his 39th birthday.

“There was less than 5 seconds from the time of the first shot until the last shot,” Owen said at a news conference Tuesday.

Investigators found a note at Ibssa’s Knoxville apartment in which the gunman said the doctor had implanted a chip that was being used to track his movements, Owen said.

Ibssa had a successful appendectomy at Premier Surgical Associates in November 2001 and suffered no complications, according to a statement from CEO Kevin Burris.

Haloperidol, an antipsychotic medication used to treat schizophrenia and Tourette syndrome, was also found at Ibssa’s apartment, but investigators believe he hadn’t been using it, Owen said.

Owen said relatives had him committed for mental treatment in February.

Also found during the search were a second handgun, a bag of marijuana and a copy of the book “The Official CIA Manual of Trickery and Deception” — a reproduction of a Cold War-era CIA handbook on the use of illusion and deception for acts of espionage.

The gun used in the shooting had been reported stolen in March, while other one had an altered serial number but wasn’t reported stolen. Police were not sure how Ibssa obtained either gun and said he did not have a handgun permit.

Police said Ibssa operated a convenience store near downtown Knoxville, which was closed Tuesday.

On Monday, a cab driver picked Ibssa up outside his apartment building, and the gunman told him to take him to the western side of Knoxville, eventually specifying the medical center.

Cab driver Freddys Sakhleh said Ibssa said seemed angry and depressed and said little about himself.

He took Ibssa to the medical center tower and waited for him to come back, and then took him to the discharge area of the hospital. The driver said he watched in horror as Ibssa pulled out a gun from his waist and started shooting.

Owen, the police chief, said Ibssa fired four shots at people exiting the building, hitting the three hospital workers. The gunman killed himself with a fifth shot. Police said it doesn’t appear he knew the women.

The two women who survived the shooting were taken to the trauma center at the University of Tennessee Medical Center. Owen said Tuesday afternoon the women — Ariane Reagan Guerin, 26, and Nancy Chancellor — were in stable condition.

The woman killed was Rachel Wattenbarger, 40. Her father, Ray Wattenbarger, said she had worked at the hospital for about five or six years, helping discharge the elderly.

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Associated Press writer Sheila Burke in Nashville contributed to this story.