The incident happened just after 8 p.m. CT when two men outside the Starbucks in the city's Uptown neighborhood met for a transaction, possibly a drug deal according to Chicago Police Commander Marc Buslik, and one of the men ran into the coffee shop.
The suspect pursued the man into the Starbucks and opened fire, killing him and striking two other people inside, police said.
One of those struck was a 12-year-old boy, who was hit in the groin and taken to the hospital in stable condition, according to authorities. The other bystander took himself to the hospital and was listed in serious condition.
Police say the suspect and victim in the shooting knew each other.
The suspect is still on the loose.
Anthony Guglielmi, chief communications officer for the Chicago Police Department, said on Twitter the shooting was not random.