Four Kenyan medics have been suspended after cutting open the skull of the wrong patient at a hospital in Nairobi.
One patient needed surgery for a blood clot on the brain, the other only non-invasive treatment for swelling.
But a horrifying mix-up of identification tags saw the wrong man operated on, reports say.
The doctors did not realise their mistake until "hours into the surgery, when they discovered there was no blood clot", the Daily Nation
The head of the Kenyatta National Hospital said the patient was "in recovery and progressing well" and an investigation is under way.
The board regulating medical practice says such a mix-up is a first in the country. It has demanded a report from the hospital and plans to hold a hearing.
Social media users have expressed shock that such an incident could have been allowed to happen.
Hospital CEO Lily Koros said the hospital "deeply regrets this event and has done all it can to ensure the safety and well-being of the patient in question.
"We are happy to inform the public that the patient is in recovery and progressing well," Ms Koros added.
She said four staff - the neurosurgeon, ward nurse, theatre receiving nurse and anaesthetist - had been suspended.
"The management has suspended the admission rights of a neurosurgery registrar and issued him with a show-cause letter for apparently operating on the wrong patient," Ms Koros said. A show-cause letter requires a staff member to account for his or her actions.
But the doctor's colleagues have protested against the suspension, reports The Star, arguing the person who put on the identification tag is the one that should be punished.
Meanwhile, the doctors' union defended staff, saying the hospital was "overwhelmed" by staff shortages and inadequate operating theatre space.
"You find one doctor could be doing 10 to 19 operations [in a day]," Ouma Oluga, chief executive officer of the Kenya Medical Practitioners, Pharmacists and Dentists' Union, told Reuters news agency.
The Nation reports that - "in a miracle of some sort" - the two patients are in good condition. It adds that the person who had the blood clot might not need to undergo surgery after all, as his condition has improved significantly.