A video of the well-built male doctor knocking out the patient in Belgorod has emerged online.
The man died, while his companion, who tried to stand up for him, was also brutally beaten by the doctor. The incident happened on December 29.
The violent attack was captured by the hospital security camera, and emerged online days later, with some 700,000 people having watched it in a day, Russia's RT television reported.
When another man who accompanied the patient to the hospital tried to interfere, he was also brutally beaten by the doctor.
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Shouting "have you understood me?" the doctor kept hitting both men while they were on the floor. Nurses pleaded for him to stop.
After the enraged doctor eventually left the room, a woman's voice -- apparently the offended nurse's -- can be heard explaining to her colleagues behind the door that the patient was asked to lie down calmly during a procedure, but did not follow her orders.
In the next eight minutes, the nurses summon an emergency room doctor to the scene, while the doctor who hit the patient attempts to bring him back to life.
The man is then seen being dragged from the camera's view, while a cleaning lady washes the floor. The emergency doctor never appeared in the video.
The man died of a head injury, officials said. He reportedly arrived in the hospital with complaints of stomach pain.