It's more than a couple, and it's been going on for a LOT longer than the media lets on. They just wouldn't talk about it when Daley was in office.
People used to claim that you'd be safe downtown, or where there were lots of people. Now that's clearly untrue. Any place where there are lots of people has become MORE dangerous, since crowds allow these "flash mobs" to "hide in plain sight", coalesce for an attack, then disperse.
You really have NO effective, legal means of self-defense in Chicago, certainly not a gun, and certainly not against multiple assailants.
The Chicago PD is NOT going to "protect" you. Regardless of intentions, they CAN'T.
If it were me, I'd avoid purely optional trips to Chicago, especially to large venues where lots of people gather, at least until Emmanuel gets this clearly ORGANIZED criminal activity under control. I wouldn't hold my breath waiting.