Soon after she boarded an MRT train with her family on Wednesday afternoon, a child's screams pierced the air.
The student, who wanted to be known as Lulu, 17, then watched in horror as a little boy ran towards the last carriage of the train.
The child, who appeared to be about nine years old, was trying to get away from an elderly woman who was chasing him while swinging an umbrella wildly.
Lulu said she saw the umbrella hit the crying boy a few times just as he reached her carriage and was cornered.
His pursuer continued her vicious attack with the umbrella as the boy screamed in pain and passengers looked on in horror.
Lulu said she was heading to Changi City Point mall with her grandmother, father, five-year-old sister, and brother, 14, when the incident happened at about 5.30pm.
She told The New Paper yesterday: "They ran from the centre cabin all the way to the back. He squatted when he found out that he was trapped. I felt very sorry for him.
"The woman, who was in her 60s, beat him all over the body with the umbrella until the handle broke. He was screaming and we were all very shocked."
An 11-second video of the beating was posted on citizen journalism portal Stomp. It shows the woman gripping the metre-long umbrella with both hands and swinging it at the boy.
In those 11 seconds, she hits him seven times and his hysterical screams are enough to send a chill down the spine of anyone watching the video. But Lulu said the attack was much longer than shown on the video, and the boy was hit more than 10 times.
She recognised the boy as she had boarded the train at Tampines station at the same time as him. He was with three adults - his attacker and a couple in their 40s, she added.
Lulu said that even before the attack started, she could hear shouting from a few carriages away.
"I heard the boy saying that he wanted to go shopping and didn't want to go home. The old woman replied, 'If you don't want to go home, you can go and die.'
"Then the beating started. They spoke in a mixture of Hokkien, Mandarin and English."
Lulu said the younger woman in the boy's group walked to the rear carriage and watched the assault.
"She just stood there and didn't try to help the boy. The man didn't even come over.
"The other passengers were shocked, but they didn't try to help. I think they were too stunned to react or were too scared to come forward as the elderly woman looked really angry," she said.
As Lulu sat petrified in her seat, her father decided to step in.
Identifying himself as Mr Tony, 42, he said: "My younger girl turned pale when she saw the attack and I felt very sorry for the helpless boy.
"I told the woman that I would call the police if she didn't stop. She replied defiantly, 'Go ahead. I will be waiting for them to come'." Lulu said the woman stopped her attack, but told her victim: "You will kena ('be punished' in Singlish) more once we get home."
Soon afterwards, she appeared to have cooled down and took a seat as the crying boy stood nearby, said Lulu.
Lulu said her family and the boy's group both got off the train at Tanah Merah MRT station and took another train bound for Changi airport.
"My family and I got off at Expo MRT station while they remained on the train heading to the airport," she said.
Responding to queries, SMRT said that in cases of distress, commuters can alert its staff via the emergency communication button.
Mr Patrick Nathan, SMRT's vice-president of corporate information and communications, said: "Where necessary, we will alert transcom police officers and assist in investigations.
"Commuters should also take socially responsible steps to offer assistance, especially where immediate help may be needed or sought by fellow commuters."
The woman, who was in her 60s, beat him all over the body with the umbrella until the handle broke. He was screaming and we were all very shocked. - Lulu, 17
Lawyers: Woman could be charged with causing hurt
The elderly woman committed an offence as she assaulted a defenceless child, said lawyers after The New Paper told them about the case.
Mr Rajan Supramaniam from Hilborne Law said she could be charged most likely with voluntarily causing hurt.
"In cases like this, members of the public should step in to protect the child. They must also inform the police about the incident," he added.
Mr Nirmal Singh, from Raj Kumar and Rama, said if the boy went for a medical check-up and the doctor found he has serious injuries as a result of the beating, the woman could even be charged with voluntarily causing grievous hurt.
"If there is evidence to show that she has been abusing the boy over a period of time, she may even be charged with ill-treating a child under the Children and Young Persons Act."
Mr Louis Joseph, from Regent Law, had similar views, saying: "It is an offence whenever an adult assaults a defenceless child."