Thavisha Lakindu Peiris, 25, was found slumped at the wheel of his car on Sunday evening in the Southey area of the city.
His manager at the nearby branch of Domino’s Pizza, Ravi Marripudi, said Mr Peiris has not been feeling well that evening and he had agreed to make one last delivery before going home.
Mr Marripudi said he set off to take the pizza to Southey Crescent - about a mile from his base - at about 9.50pm.
But 15 minutes later he got a call from the customer saying the order had not been delivered and there were voices outside.
The manager said he sent another driver to look for Mr Peiris and he found his colleague unconscious in his Toyota Yaris, in a residents’ parking bay near the delivery address.
“It is so shocking,” Mr Marripudi said.
“He was such a kind person.
“If someone had wanted money, he would not have fought. He would have handed it over.
“He was just a really nice person.”
Mr Marripudi said the incident had worried delivery drivers and four have decided to quit since the murder.
“He wasn’t feeling very well and he wanted to go home but he said he would deliver this last one,” he said.
Mr Peiris came to the UK from Sri Lanka to study IT at Sheffield Hallam University.
He graduated in 2011 and had started working at Domino’s to help fund his studies.
Mr Marripudi said: “He was very excited about his new job.”
A 50-strong police team is now working on the murder inquiry.
The police officer leading the investigation, Detective Superintendant Lisa Ray, said her team did not know why Mr Peiris had been killed.
She said she could not rule out any motive, including robbery, although she said a small amount of cash was still with him in the car, which did not have Domino’s livery.
The detective said a “career-minded, hard-working, bright, articulate and friendly young man” suffered a “brutal and shocking death”.
She said: “Thavisha Lakindu Peiris was a bright, hard-working, intelligent and caring man who had worked hard to develop his career in Sheffield.
“His murder is an absolute tragedy and has caused untold grief for his mother, father and brother in Sri Lanka and for his many friends in Sri Lanka and in Sheffield.
“Everything we have learned from his family, friends and workmates at Domino’s suggests he was a career-minded, hard-working, bright, articulate and friendly young man who was very much planning his future. To date, we have found no explanation for his brutal and shocking death.
“I need to hear from anyone who knows anything about his murder.”
Mr Peiris’s family are preparing to travel to South Yorkshire, police said.