Mr Tong Ming Ming, 34, was on a tea break during reservist training in early March when an SMS and a Facebook post by his secondary school friend Regina Lim caught his eye.
She wrote that a mutual friend's colleague was likely to die within days if he did not receive a liver transplant. The family was urgently looking for a living donor who, among other things, had to weigh 80kg or more. Could anyone please help?
Mr Tong, a big, burly cabby and former police officer, messaged his old friend immediately to find out more.
The patient, civil servant Toh Lai Keng, 43, from the Ministry of Home Affairs (MHA), was a colleague of their mutual friend from their Peicai Secondary School days, Ms Leow Shee Yin.
Within minutes, Mr Tong was on the line with Ms Leow. "She was in tears, saying the illness was very sudden and that he had a very young son," recalled Mr Tong.
By then, Mr Toh's wife, Samantha, 40, and brother, Jeffrey, 42, had failed the tests to be donors.
"Time was running out. I just knew that I had to help," Mr Tong recalled.
He made that decision on March 11. After four days of tests, checks and interviews, he underwent a nine-hour operation at the National University Hospital (NUH) to donate most of his liver to Mr Toh on March 15.
Today, nearly five months on, both donor and recipient are doing well.
The Ministry of Health confirmed that this was the first altruistic liver donation here by an unrelated living donor - someone with no blood or emotional ties to the patient.
To most people, including the man who received the gift of life, the genial, soft-spoken bachelor's generosity is beyond comprehension.
"What can I say? He's a great man," said Mr Toh, his voice tinged with emotion. "Human beings are selfish. I can't think of anyone else who would do this for a stranger."
Before his brush with death in March, Mr Toh, a food-loving father of a three-year-old son, had no history of liver problems. In fact, when he first fell ill with high fever and was hospitalised at Tan Tock Seng Hospital in early March, he thought he had dengue fever.
But tests showed his liver was failing rapidly. By March 7 - a Thursday evening - he was transferred to NUH which has liver transplant facilities. By the following Tuesday, he was in a coma.
The cause of his liver failure remains unknown. "They told my wife I had a week to live," said Mr Toh.
It was serendipitous that his colleague, Ms Leow, confided in her friend Ms Lim about his desperate situation, and that Ms Lim in turn went on Facebook, and her post touched Mr Tong.
The cabby needed extensive tests and interviews, including one with an independent ethics committee, to ensure he was psychologically sound, not coerced and no money had changed hands, before the operation on March 15. The risks of the procedure were also explained to him.
"Things just fell in place when Ming Ming came on the scene," said Mr Toh, a deputy director at MHA. "I guess it was a miracle."
Both men hope their experience will show others that much-needed organs can come from people who are not friends or family. "With his kindness and generosity, Ming Ming has shown that even strangers can step forward to save lives," said Mr Toh.
Since the operation, the men have visited each other at home, shared meals and are now friends.
They also discovered a long-lost kampung connection - the extended Toh and Tong families used to live near each other in the Braddell area when they were children. "It's really unbelievable," marvelled Mr Toh.
Ask Mr Tong why he stepped forward and he points heavenwards. "It's a calling," he said with a laugh, referring to his Christian faith.
But dig deeper and other reasons pour forth.
Having grown up with an absent father, he kept thinking of Mr Toh's wife and young son, Terence, who could have lost his dad before even getting to know him.
Also, he was satisfied that the procedure would be safe. "The liver can grow back, so I will be fine," he said.
"As a cabby, there is probably a greater chance of dying in a road accident," he added with a laugh.
Friends like Ms Lim and Ms Leow, both 34-year-old mothers who met Mr Tong in school more than two decades ago, are not surprised by his large-heartedness.
"When we were urgently looking for a donor, I did not think of Ming Ming," said Ms Leow. "But in hindsight, if anyone could have done this, it was him."
She remembers his zeal to help others during the compulsory community involvement programmes of their schooldays. "Most of us stopped volunteering after secondary school, but Ming Ming never gave up. He really, really wants to help others," she said.
A graduate of Temasek Polytechnic, Mr Tong has long been hooked on helping. As a taxi driver since January, he has ferried amputees for medical appointments, kidney patients for dialysis and poor older folk to church.
He said he usually waives the fare, but some regular passengers pay a token sum.
He has donated blood in response to urgent appeals, helps to clean homes of the elderly in one- room rental flats in Upper Boon Keng, and leaves food packets for immobile old people in Chinatown.
"There is a lot of need in Singapore if you know where to look," he said. "I do what I can to help."
His choice of jobs so far also reflects his passion to do good. As a boy, he saw police officers coming to his family's three-room Hougang home when they were harassed by loan sharks. His cabby father, a gambler, would chalk up huge debts.
"The officers were kind and would protect us. From then on, I always wanted to be an officer," he said.
He joined the police force after graduation in 1998. He has also worked in the social service sector, looking after abandoned, abused and delinquent children.
The youngest of three sons also recalled how his parents and grandparents were forced to sell their adjacent HDB flats to settle his father's gambling debts.
His role model is his mother, Madam Neo Teng Huay, 63, who raised her sons by working 12 hours a day selling curry puffs in a coffee shop. "She has faced hardship, but is never bitter. She always helps others."
Mr Tong said that although the family always had food on the table, his hardscrabble childhood has helped him form lasting bonds with some of the bruised and broken boys he encountered while working in youth homes.
Many may think that with so much hardship and suffering, it is impossible to change the world, but Mr Tong said: "If you can help even one person in need, you would have done just that."