Passers-by found his body over two hours after the incident and informed police.

On Monday night, Johnson (20) of Baba Koil Street, Maraimalai Nagar, was crossing the tracks below the road overbridge near Pallavaram railway station, when he heard a woman, breastfeeding her child, crying out for help. The miscreants were trying to drag her from the railway station when he intervened.

“During our investigation we learnt that a group of four men were molesting the fruit vendor – a 30-year-old woman. They pulled her hand repeatedly. When Johnson noticed it, he rushed to her help,” a Government Railway Police officer said.

“He punched Karthik (one of the four youth) and managed to save the woman, who rushed back to her child and then went home,” he added.

Karthik then reportedly pulled out a knife and stabbed Johnson, who fell down. Karthik and the others stabbed Johnson repeatedly and left him in a pool of blood.

While Johnson’s act of rescue and the subsequent attack on him happened at about 9 p.m. Monday night, police sources said that passers-by noticed the youth lying amidst the bushes at the northern end of Pallavaram station’s platform much later and informed them.

Poor illumination along the stretch could be a reason for the delay in discovering Johnson’s body, locals said.

Johnson, a painter by profession and a daily-wage labourer, was on his way to the station to board a train to go home when the incident happened.

The four suspects — Karthik, Sathish, ‘nondi’ Sullan and another man who is yet to be identified — are at large. Police say they were drunk at the time and only minutes before this incident, the four of them had assaulted Ramamurthy (25), before stealing Rs. 5,000 and a mobile phone from him. The victim had just got down at Pallavaram railway station to go to his home in Pozhichalur.

“It is clear that Johnson’s gesture helped the woman get away. She possibly could even have seen the victim being assaulted, perhaps not very well, as she was at a distance,” police said.

A team from GRP station, Tambaram reached the spot at about 11 p.m. on Monday, after they received information about two hours after the incident and took Johnson to the Tambaram Taluk Government Hospital in Chromepet, where doctors pronounced him dead on arrival. He had several stab injuries in the chest, abdomen and back, police said.