A doctor with terminal cancer killed a female paediatrician and then himself after taking hostages at a children's clinic in Austin, Texas.
Dr Bharat Narumanchi held hostages in a five-hour siege before killing Dr Katherine Lindley Dodson.
Narumanchi had applied for a volunteer position at the clinic a week ago and was declined.
He later came back carrying a pistol, a shotgun and two duffel bags.
Police spokesman Jeff Greenwalt said Narumanchi had recently been given "weeks to live" after a cancer diagnosis.
He said: "The case as far as who did this is closed. We know who did it. And we know that there's no longer a threat to the public. But we really, really want to answer the question of why."
Dr Lindley Dodson, 43, was beloved by patients and their families.
Karen Vladeck, whose two children were among her patients, told the Austin American-Statesman: "You saw her at your worst when your kid was sick, and she just always had a smile on her face.
"She made you feel like you were the only parent there, even though there was a line of kids waiting."
During the siege a SWAT team used a megaphone to communicate with the armed doctor.
A hostage negotiator shouted: "Your life is very important to me. And I know life is very important to you.
"You don't deserve to go through this. For all you have done for others. That is why I want to help you work through this. You have saved a lot of lives."
Police first sent in a robot and then officers went into the medical office where they found two bodies.
They did not comment on how the two doctors died.
A police spokesman said: "The SWAT situation has ended. Two subjects have been located and were pronounced deceased."