Segalovich, centre, with the press at a product launch in May, two months before a tumour was found in his brain.
Ilya Segalovich, co-founder of the Russian Internet search engine Yandex, lost his fight with cancer on Saturday in a London hospital, after the doctors turned off the life support machine that had kept his heart beating for three days.
He was 48 years old.
"Last week, a tumor was discovered in [Segalovich's] head. On Tuesday and Wednesday, cancer spread to brain membranes. Malignant meningitis lead to irreversible consequences — his brain burnt out in less than 24 hours," Yandex CEO Arkady Volozh said in a statement on the company's blog on Sunday.
Segalovich fell into a coma and was declared brain dead on Thursday, July 25, but doctors decided to keep him on life support, hoping for a marvel.
"We couldn't make a miracle happen," Volozh said, "but we could give it a chance. We lost all our hopes on Saturday night. Even a body as strong as [his] couldn't bear it. His blood started to develop changes incompatible with life. We had to let him go with dignity."
Segalovich, an entrepreneur, software engineer and philanthropist, with his joyful approach to life and work, won respect from fellow Internet programmers, businessmen and government officials.
Following news of Segalovich's coma, Prime Minister Dmitry Medvedev wrote on his Facebook page that his death would be a loss for the entire Internet industry in Russia. "Ilya Segalovich," Medvedev said, "is a story of success that can and must be taken as an example, especially by young people. A high class professional with a kind heart and an ability to inspire and care for those around him."
It is not only the Internet community that will miss Segalovich's charisma. The country's less fortunate children will also feel the loss of his input.
The Yandex founder was an active participant in his wife's Maria Yeliseyeva's charity, Maria's Children. He contributed his time and money to supporting the group's work with Russian orphanages, helping children get educated and organizing foreign exchange programs.
He often visited children hospitals as part of a troupe of clowns entertaining patients.
Ilya Valentinovich Segalovich was born on September 13, 1964 in Nizhny Novgorod. In 1986, he graduated from the Russian State Geological prospecting University with a degree in geophysics.
Between 1993-96 Segalovich, together with his classmate Arkady Volozh, developed a text indexing technology that was able to search through the Bible and Russian classical literature, taking into account morphological nuances in the Russian language. This technology was to become a foundation for a search engine, Yandex.ru, launched in 1997.
In 2000, Segalovich co-founded Yandex, becoming chief technology officer. That same year the new company secured a $5 million investment from ru-Net Holdings in return for a 35 per cent stake.
Yandex went public in 2011, raising $1.4 billion in an initial public offering on the Nasdaq exchange under the ticker YNDX.
The company, currently valued at about $10 billion, operates the most popular Internet search in Russia with a market share of 61.7 percent, well ahead of competitors Google and Mail.ru Group.
Segalovich is survived by his wife Maria Yeliseyeva and four children.