Jemel Roberson

Illinois state police on Tuesday were investigating a white officer over the fatal shooting of a "brave" black security guard who had apprehended a suspected gunman at a bar outside Chicago, officials said.

It began in a way gun advocates have suggested would curtail violence. A gun comes out. Shots are fired. A "good guy with a gun" steps in to help before police can respond.

Illinois state police on Tuesday were investigating a white officer over the fatal shooting of a "brave" black security guard who had apprehended a suspected gunman at a bar outside Chicago, officials said.

It began in a way gun advocates have suggested would curtail violence. A gun comes out. Shots are fired. A "good guy with a gun" steps in to help before police can respond.