According to the police, the incident took place in Civil Lines area of North Delhi on Thursday night.
The attacker, identified as Suraj, has been arrested.
"At the time of the incident, Suraj was roaming in Punjabi Basti area when John, who had some problem in walking, accidentally stepped on Suraj's slipper from behind and broke its strap," said a police official.
Although John apologised and said that it happened accidentally, Suraj started abusing him, took out a knife and stabbed him in his chest.
A police team reached the spot after a PCR call from an auto driver who saw the incident, he said.
John was rushed to a nearby hospital where he breathed his last.
"Suraj was nabbed from Chhan Basti in Timarpur area. The knife used in the crime was also recovered from his possession," he said.
