Prosecutors say although Kenneth Bardlett, 20, was not the triggerman, he was involved in the crime and has admitted to it.
Bardlett was charged with first degree murder and attempted armed robbery in connection with the shooting death of Hussein Saghir at Sam's Tobacco and Food Mart on January 19.
36-year-old Hussein Saghir was fatally shot during the botched robbery. At the time, Saghir was closing the shop for the evening with his brother.
Surveillance video caught the entire crime, showing two men trying to force the brothers back into the store. Prosecutors say Saghir refused to go back into the store because his 3-year-old nephew was inside.
Saghir's family welcomed news of the arrest, thanking investigators. They released a statement that said, in part: "We urge the public to remember that the triggerman remains free and we are pleading to anyone with information to please come forward and contact Bensenville police."
Bardlett has a criminal record and allegedly confessed to being one of the robbers on the surveillance tape, but his cousin, Andrea George, told reporters Wednesday morning that she believes he didn't do it.
''I don't think Kenneth admitted to anything he didn't do so therefore I don't know about that,'' George said.
Police were tight-lipped about whether they are close to making another arrest, and how they tracked down Bardlett.
"Very difficult for me to get into this information because it's still an ongoing investigation and we don't want to jeopardize it," said Chief Frank Kosman, Bensenville Police Department.
A $10,000 cash reward is being offered in the case. The Bensenville store remains closed.