Travell Taylor faces one count of first-degree murder. Chicago police said Friday that Taylor was positively identified as the gunman.
Mills, 26, was shot multiple times in the 4100-block of West Roosevelt Road just before 1:30 p.m. Monday, police said. He was pronounced dead at the scene.
Mills, a father of two daughters, played with Southern Miss in the NCAA Tournament in 2012. After college, he played basketball overseas. He most recently stood out on the MBL team the Chicago Fury.
"His thing was basically trying to get his self situated to make big money to take care of his family. That's all he talked about," said Chicago Fury coach Maurice Carter.
"He was like a son to me," North Lawndale assistant coach Terry Johnson said. "It's unbelievable. Everyone is just at a loss for words, such a great, great guy."
A 2009 North Lawndale graduate, Mills kept tight ties with the school. He helped lead the Phoenix to the 2008 Class 2A state championship and the 2009 city title.
"Jon spoke to our teams so many times about what it takes and how to grow up in this type of atmosphere," said North Lawndale assistant coach Terrence Redmond said. "It's tough. He loved this city and he represented Chicago throughout the United States."
"My heart is pierced because it is real sad to think the pain is mother is suffering now," Brown said.
Taylor will appear in bond court Saturday morning.
The Sun-Times Media Wire contributed to this report.