BROOKLINE (CBS) - "Please cover your face" says the sign on the door of the Dunkin' on Harvard St. in Brookline. Like many communities in Massachusetts, Brookline has a mask mandate for businesses.

When 23-year-old Dion Millsap, who's from Boston stepped in, police say he threw hot coffee at a customer who did not comply.

Officers could be heard on a scanner recording asking the police dispatcher about it. "Did you say he threw a coffee on the person?" "Roger, hot coffee he threw at him."

Millsap was arraigned on charges of disorderly conduct, and assault and battery with a dangerous weapon.

"Once the defendant turned around and noticed that the victim didn't have a mask on, the defendant made a comment about it," Assistant District Attorney Philip Czarnec said in court.

"To me, this is a disorderly conduct charge that has been blown way out of proportion," said defense attorney Ian Henchy.

It's the latest in a string of incidents stemming from frustrations over masks.

At Boston's North Station Tuesday, Transit Police say a man named Rutal Jaiswal, who's from Sturbridge, tried to ride a train without a mask. When they escorted him out, they say he hit them.

"I really don't know why someone would get so agitated over putting on a mask. It's only to ensure everyone else's safety including yourself," said passenger Josh Goldenberg, as he waited for a train.

At the North End's iconic Pizzeria Regina Sunday, police say a customer punched an employee in the face after he was told to wear a mask.

Tensions are even making it into government meetings. In Braintree last week, a school board meeting was abruptly adjourned when board members showed up maskless.

Also last week, New Bedford town councilors had a heated exchange.

"As you sit here with no mask, while all the rest of us have our masks on," said Linda Morad to a fellow councilor. "Inappropriate, totally inappropriate!"