KNOXVILLE, Tenn. - A mentally ill gunman who killed a hospital worker and wounded two others was upset with a doctor he thought had implanted a monitoring device during an appendectomy in 2001, police said Tuesday.

Knoxville Police Chief Sterling Owen IV said gunman Abdo Ibssa (AB'-doh IHB'-sah) first entered a medical tower near Parkwest Medical Center and asked for the doctor who performed the appendectomy. He then went to another area where patients are discharged and opened fire. He killed himself after shooting the three women on Monday, 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.

Owen said 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 the patient's movements.

Medication used for treating a psychological condition was also found at his apartment, but investigators believe he hadn't been taking his medicine, Owen said. Owen said relatives of the naturalized citizen from Ethiopia had him committed for mental treatment in February.

A copy of the book "The Official CIA Manual of Trickery and Deception" was also at his apartment.

Cab driver Freddys Sakhleh has said he picked up the gunman outside an apartment complex, and the man told him he wanted to go to the western side of Knoxville. They stopped at an ATM, where the suspect withdrew $20 before telling Sakhleh to take him to the medical center complex.

Sakhleh said the man said seemed angry and depressed and said little about himself, only that he was from Atlanta.

Sakhleh said he was directed to take the man to the medical center tower and told to wait for him to come back. When his passenger returned, Sakhleh said, he told the driver to take him to the hospital entrance where some patients are discharged.

Sakhleh said the man then got out of the cab, handed him $20 and told him to wait five minutes. He returned, grabbed a gun from his waist and started shooting.

"I called 911, and I said, 'Please send some people here, this man is shooting like crazy,'" Sakhleh said. He said the gunman then shot himself in the head.

"All of this happened in a matter of seconds," the driver said.

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 were in stable condition.

The women's families issued statements expressing thanks for prayers and support.

The family of Ariane Reagan Guerin, a 26-year-old employee at Parkwest, said they were hearing promising information about her prognosis. The family of Nancy Chancellor, 32, said she was doing well.

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. He said he would remember his daughter's smile.