The man, aged 28, is believed to have been stabbed more than once as a group of men stole his black Toyota estate from outside high-rise flats in Lower Derry Street at around 7.15pm last night.
The injured man managed to make his way to the McColl's shop around 100 yards away where he collapsed outside the entrance before being helped by staff who called police and an ambulance.
He was taken to hospital where he continues to be treated today. His injuries are thought to be serious but not life-threatening.
A woman who lives at a nearby block of flats described seeing paramedics treating the victim in the shop entrance.
Gemma Bodycote, 27, told the Express & Star: "I went to the shop about 8.30pm to 9pm, but he was already lying there.
"The man was positioned between the two doors (at the entrance). He didn't look good, I didn't think he was going to make it.
"He was Asian. He was covered in blood. It wasn't nice at all to see.
"There was fire crews, a lot of police and the ambulance was working on him, trying to save his life.
"This type of thing doesn't happen around here. You hear of people getting beaten up but not stabbed."
Two police cordons were in place throughout the evening: one around the car park where the attack happened and a second outside McColl's, which was closed in the aftermath of the attack.
Photos taken at the scene showed a pool of blood left on the steps to the shop next door to the Rock Fryer on Hill Street.
No arrests have been made and West Midlands Police today appealed for anybody who may have witnessed the incident to get in contact.
Det Sgt Leighton Shingles, from CID, said: “Were you in the area at the time and saw what happened? If so please help us and get in touch.
“Maybe you have dashcam footage or have seen the car - a black Toyota estate registration N529 YEO - we need your help to catch those responsible.”
Detectives are not yet certain of the number of attackers involved and were not able to offer a description of the suspects.
A man, who gave his name as Mr T Cartwright, said he witnessed a man being chased by a gang with balaclavas earlier the same day.
The 64-year-old from Wall Heath said he was by the Top Lock, on Brierley Hill's Waterfront, when he saw a the man being chased. It is not clear if this incident was linked to the carjacking.
Mr Cartwright told the Express & Star: "A gang of them people were chasing a chap down there. He shouted us to help him and they (the gang) took pulled their balaclavas off and ran off."
A spokesman from West Midlands Ambulance Service said: "We were called at 7:17pm last night to reports of a stabbing on Hill Street in Brierley Hill.
"We sent one ambulance, a paramedic officer and Merit Trauma Doctor to the scene.
"We treated one patient, a man, for injuries not believed to be life threatening.
"He was taken on blue lights to the hospital for further treatment.”
Anyone with information is asked to contact police via live chat on the force website or by calling 101 quoting crime reference number 20DY/11389Z/20.