Video of part of the incident
shows a white man spitting at a black man, telling him his children are "disposable vermin" and calling a second black man a slave.
Boucher also punched a 59-year-old man unprovoked, authorities said. The older man was taken to a hospital with an eye injury, CNN affiliate WLS-TV
Boucher has been charged with three counts of misdemeanor battery. He is scheduled to appear in court July 5.
Boucher could not be reached for comment Thursday.
An emailed statement from a Starbucks spokeswoman said: "We have absolutely no tolerance for this type of behavior in our stores, and are grateful to the partners (employees) and customers who stepped in to help until officers arrived."
It wasn't immediately clear who spilled the coffee. A WLS photographer recorded a video of what followed.
In the video, Boucher said: "You're disgusting," to an unidentified man after the coffee-spilling incident.
A Starbucks employee appears to intervene, standing between Boucher and the unidentified man.
"I was shocked because I thought it was going to ... end right there, security was going to come, the cops were going to show up," Starbucks employee Juan Torres told WLS.
Outside the store, Boucher walked up to an unidentified black man who, in addition to the WLS photographer, was videotaping the incident. Two bystanders stepped in between the men, according to video.
"Your children are disposable vermin," Boucher said to the unidentified black man before walking away.
"Shut up, slave. Do not talk to me," Boucher said to a second unidentified black man who approached him, the video shows.
A bystander seemed to push Boucher away, trying to calm him.
Boucher then spat at the man whose children he had called "disposable vermin," the video shows. One bystander stood between Boucher and the man as the two appeared to try to fight.
"Get on all fours right now. ... Do not walk off on two legs," Boucher said to the unidentified black man.
Boucher then walked away. Shortly after, he was seen punching another unidentified man walking in his direction. The man falls to ground in the video.
The man Boucher spat at in the video helped detain him until police arrived, authorities said. The video shows bystanders also tackling Boucher.
"Calling people ... racist slurs when I was coming into work, I was not expecting to see that," Torres said.