Police said the 39-year-old truck driver was making a delivery at the Northland Party Shoppe on the corner when a black man approached him with a weapon.
He fired several shots at the deliveryman, police said, hitting him in the stomach.
Police say surveillance video from the area shows the suspect walk into the back of the delivery truck when the driver was still inside. A three-minute confrontation between the men ensued. The shooter rolled out of the truck and fled on foot.
"The driver works his way out of the back of that vehicle at some point and collapses on the berm of the grass," said Detroit police Inspector Vicki Yost.
The video also shows a man in a green T-shirt walking nearby when the shooting happened. The man seemed to take interest in what was going on inside the truck but he kept walking. He returned later, but again walked away. Investigators want to talk to him.
Detroit police transported the victim to a nearby hospital where he was listed in critical condition. He was at Sinai-Grace Hospital Wednesday night.
Police were actively searching for the shooter. They did not release a better description.
Anyone with information on the shooting is asked to contact the Detroit Police Department at 313-596-5628 or Crime Stoppers at 800-SPEAK-UP.
-- Detroit police would like to speak to a man wearing a green T-shirt which surveillance video shows near the truck during the shooting.