Fr. Michael Pfleger said Saturday that the shooter would not hold the community in fear.
The victims were taking part in anti-violence activities at the church gym. Police say they stepped outside, there was an altercation, and the teens were shot.
Pfleger asked for anyone with information to come forward.
"We have to catch the person. I mean, he stayed in somebody's house last night. And you can't do that. You can't shoot young people and get away with it and hide and go on with your life. It's not acceptable. We're not going to tolerate it," said Pfleger.
"It's a very sad commentary that, at a church, at a basketball game on a Friday night, this kind of violence can find its way to two young men," Chicago Police Supt. Jody Weis said.
A $5,000 reward is being offered to anyone with information that leads to an arrest.