Friends were signing letters and leaving flowers at a growing memorial at the scene of the crime Sunday.
Police say the victim, Dennis Fox, 53, was reportedly trying to stop a robbery at the CITGO on South Pulaski when he was stabbed and then shot.
Kaz Link, 33, was arrested at the scene and charged with first degree murder. According to a police report, officers who rushed to the scene found Link in bloody clothes with blood dripping from his hands.
The victim's father says Fox had worked at the station for about five years.
Link is scheduled to appear in court Monday.
The Sun-Times Media Wire contributed to this report.