(CNN) -- A doctor who was on the front lines fighting the Ebola outbreak in Sierra Leone has died from complications of the disease, Doctors Without Borders said Tuesday. Dr. Sheik Humarr Khan fell ill early last week while overseeing Ebola treatment at Kenema Government Hospital, about 185 miles east of Sierra Leone's capital city, Freetown. He was treated by the French aid group Medecins Sans Frontieres -- also known as Doctors Without Borders -- in Kailahun, Sierra Leone, up until his death, spokesman Tim Shenk said. "RIP Dr. Sheik Humarr Khan," wrote one of the many people who remembered Khan fondly on Twitter. "What a hero. What a loss."
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"What a hero. What a loss," writes one admirer on Twitter
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Dr. Sheik Humarr Khan was infected with Ebola last week
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He played a key role in fighting the outbreak in Sierra Leone
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Khan fell ill while overseeing treatment and isolation centers in the country's capital
@placeholder's sincere thoughts and condolences are with Dr. Khan's family, friends and colleagues."