A four-year-old boy was crushed to death after becoming trapped under an escalator at a subway station in the Chinese city of Chongqing.

The incident took place Thursday when a woman brought her son and three-year-old daughter into the station, and left them as she attended to some business in the ticketing hall, according to the Daily Mail.

Unsupervised, the children began to play on the escalator. In the middle of playing with the handrail, the boy fell and rolled into a narrow space causing his chest to become wedged between the bottom of the rail and the floor.

The escalator didn't stop until the subway station staff shut down the escalator 20 seconds later, eyewitnesses testified. The boy was extracted around 11 a.m. and taken to the hospitals where he died from his injuries, according to the New York Daily News.

4-year-old, left unattended, was killed after getting trapped under escalator handrail in Chongqing pic.twitter.com/OJre2yYnL5

— CCTVNEWS (@cctvnews) October 9, 2015

A statement from the Chongquing Rail Transport Authority revealed the company is carrying out an investigation and offering assistance to the family, according to the BBC.

"We are deeply regretful and heartbroken over this case! We also would like to remind all passengers to look after their young children and old folks when travelling, be more alert, and avoid similar accidents!" it said.

This incident mirrors a similar one that occurred in July, when a mother died after she fell through loose metal plates at the top of an escalator to save her son in a shopping center in Jingzhou, Hubei province.

However, unlike the previous incident, which was considered a tragedy, many took issue with the mother and other commuters for not keeping an eye on the boy.

"This time it is just the adults' fault," one user said over social media.