Newly released phone recordings paint a scene of terror inside a US urology clinic where callers hid in bathrooms and exam rooms from a suicidal gunman who killed one doctor and shot another.
Callers including a woman hiding under a desk and another who whispers "he's going to ... kill us", with gunshots audible in the background, can be heard on the tapes, released on Tuesday.
Alan Oliver Frazier, 51, told patients to leave or he would shoot them after he entered the Urology Nevada office in Reno on December 17 and began firing a pistol-grip, 12-gauge shotgun.
The shooter, from northern California, said he was angry because "he had a vasectomy here and they ruined his life", a male witness told a 911 dispatcher from a locked bathroom where he and about 10 others hid.
"He says, 'As long as you're a patient, you can leave. Otherwise I'm going to shoot you,'" the man said.
The bathroom was outside the urology office where the shooting occurred.
Frazier used the shotgun to kill Urology Nevada president Dr Charles Gholdoian, 46. He also critically wounded another doctor, then turned the gun on himself.
A woman hiding under a desk was talking so softly on the emergency recording she could barely be heard.
"I hear gunshots outside my office," the woman said.
"I just heard another one ... He's going to (expletive) kill us."
"Oh, my God ... He's outside my door," she said.
Among the 50 calls police said they received was one from a woman in a locked office, gasping for breath between sentences.
"He's in the middle of the office," she said.
"We think he shot one of our doctors."
Police arrived at the scene within minutes.
They confirmed Frazier had been a patient at the facility who had complained about a botched surgery in 2010.
The unemployed former power plant worker said in a suicide note he planned the attack and his focus was on the physicians, police said.
Detectives are investigating Frazier's involvement in an internet chat room where he reportedly complained about complications from the surgery, city spokeswoman Sharon Spangler said.
She said a neighbour said Frazier told him the day of the shooting that he was leaving and not coming back.
