Officers received several calls of a shooting at Belmont and Glenn Avenues shortly after 4:00 pm.
Witnesses told police they saw someone get shot and walk out of the area. Investigators tracked down the victim at a homeless encampment a few blocks away.
Police say the man had been shot once in the chest. His condition has not been released.
Officers say the victim and another man got into an argument in an alley. The suspect pulled out a shotgun and fired at the victim's chest.
Investigators are now searching for that suspect, who was believed to be wearing a white shirt, black jeans and a red hat.
Anyone with information is asked to call the Fresno Police Department.