A 21-year-old student was killed while his friend is battling for life after they objected to a law student smoking in public. The accused, son of a visiting IIT-Delhi professor, reportedly rammed his car in their motorcycle after the altercation.

The incident took place on Sunday in south Delhi when Gurpreet Singh (21) and his friend Maninder Singh (22), both students of photography, went out at night to shoot a documentary on pavement dwellers.

At around 1 pm, they stopped at a food joint near Safdarjung hospital's casualty ward. While they were eating, one man, later identified as Rohit Krishna Mahanta, stood next to them and started smoking. The accused was reportedly in an inebriated state.

"The duo objected to the man blowing smoke on their faces and asked him not to smoke in public. The objection made Mahanta furious and he began to abuse the duo. The verbal altercation later turned violent. When locals intervened, Gurpreet and Maninder were asked to leave the place," an eyewitness told police.

But when the duo left the spot on their motorcycle, they were reportedly followed by Mahanta in his Ford Figo. The duo had hardly covered a distance of 400 metres when the accused rammed the bike from behind, also hitting an autorickshaw and a private cab in the process. Mahanta managed to flee the spot.

Both Gurpreet and Maninder fell. Passersby called the police control room and rushed them to the AIIMS trauma centre. Gurpreet succumbed to his injuries on Wednesday. "Based on the complaint, Mahanta, a resident of Defence Colony, was booked. He was arrested and later released on bail," a police officer said.

Gurpreet's family has launched a social media campaign, alleging that it was not an accident but attempt to murder. Police said the accused passed out of Jindal Law University in 2015 and is presently pracitising law as a standing counsel for Assam government.