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A man who had grown despondent over his elderly mother's failed spine surgery shot her surgeon at Johns Hopkins Hospital on Sept. 16, 2010, then killed his mother and himself during a two-hour standoff that put the Baltimore medical campus on lockdown, police said.

Baltimore police identified the gunman as Paul Warren Pardus, 50, of Arlington, Virginia. Investigators said Pardus was being briefed at his mother's bedside on the eighth floor of the hospital's Nelson building when he drew a small-caliber handgun and shot the physician once in the abdomen.

The wounded doctor was David B. Cohen, an orthopedic surgeon and assistant professor at the Johns Hopkins School of Medicine. Days earlier, Cohen had operated on Pardus' 84-year-old mother, Jean Davis, to relieve a spinal compression. The surgery left her paralyzed, and relatives said Pardus had been told she would likely never walk again.

After the shooting, Pardus barricaded himself in the room with his mother while police, SWAT officers, snipers and FBI agents surrounded the building. A witness told investigators he heard the man shout, "You ruined my mother," according to news accounts of the standoff.

When officers entered the room about two hours later, they found Davis shot in her bed and Pardus dead on the floor of a gunshot wound, police said. Police Commissioner Frederick Bealefeld said officers did not fire their weapons; an earlier report that police had shot Pardus was retracted as a miscommunication.

Cohen was taken to surgery and listed in stable condition, and hospital officials said he was expected to recover. Relatives described Pardus as his mother's primary caregiver, a former medical-transport driver who had been out of work while looking after her and who had no criminal history beyond traffic violations. The killings prompted immediate questions about security at the sprawling East Baltimore campus, one of the nation's best-known hospitals.

The recording archived with this post is police and dispatch radio traffic captured over the scanner as officers responded to the hospital during the standoff, not a caller's 911 call.