Daniel Libby was set to board a Boston-area train when a rail conductor asked the passenger for a simple request: Put a mask on.

But instead of adhering to the Massachusetts Bay Transportation Authority’s mask mandate for riders regardless of vaccination status to help curb the spread of the coronavirus, the 40-year-old man responded Wednesday by allegedly attacking the conductor who asked him to wear a face covering.

Libby, of Middleborough, Mass., was arrested and charged with assault and battery on a public official, MBTA police said in a news release. Police said the man “responded with several expletives and refused to place a mask on” at the Braintree MBTA Commuter Rail Station.

“It was then alleged Libby shoved the victim and used his shoulder to force his way into the train,” police said Friday.

Libby did not immediately respond to a request for comment Sunday. It’s unclear whether he has an attorney. His vaccination status was not mentioned by police.

If convicted, Libby faces up to 2½ years in prison and a fine between $500 and $5,000, according to Massachusetts state law.

The incident is the latest in a number of mask disputes involving travelers unwilling to follow coronavirus safety regulations that have led to a surge in disruptions in recent months. The disputes, many of which have been captured on video, have seen travelers — on planes, trains, buses and subways — yelling, fighting and being arrested over their refusal to wear a mask.

Many of the incidents have happened on planes at a time when the Transportation Security Administration has required all air travelers to wear face coverings on flights, during boarding and deplaning, and while in the airport. The Federal Aviation Administration said that more than 70 percent of the 4,385 reports of unruly passengers this year involved those who would not comply with the federal mandate to wear a face covering.

Although the FAA says the rate of such incidents is declining, the total for fines for bad behavior has already eclipsed $1 million for the year.

“We’re still a good two to three times above where we need to be,” FAA Administrator Stephen Dickson told CBS News. “And so we’ve still got additional work to do.”

In May, when the Centers for Disease Control and Prevention initially stated that “fully vaccinated people can resume activities without wearing a mask,” the MBTA issued a news release reminding travelers that “federal and state regulations continue to require face coverings while riding MBTA vehicles and within the MBTA system, regardless of a person’s vaccination status.” As the highly transmissible delta variant ravaged the country over the summer, the CDC recommended in late July that vaccinated people resume wearing masks under certain circumstances.

“Those who refuse to comply with the MBTA’s face covering requirement may be denied boarding of or be removed from MBTA vehicles and the system,” according to the MBTA’s guidelines on coronavirus protocols.

Massachusetts, which is averaging nearly 1,700 new cases a day, has seen its rate of daily infections drop by 15 percent in the past seven days, according to data tracked by The Washington Post. Close to 68 percent of Massachusetts is fully vaccinated, making it among the most immunized states in the country.

At 5:20 p.m. on Wednesday, the MBTA said officers received a call of an incident at the commuter rail station in Braintree, Mass., located about 14 miles outside Boston.

When they arrived, a rail conductor, who has not been publicly identified, told police that Libby refused to wear a mask and attempted to forcibly enter the train. MBTA officers then told the passenger he could not stay onboard.

“Officers informed Libby he had to exit the train and furnish his name as the victim [wished] to pursue assault charges,” the MBTA police wrote. “Libby refused to cooperate with the officers and would not comply with any requests.”

The Middleborough man was taken into custody on the charge of assault and battery on a public official, police said. Richard Sullivan, superintendent of the Transit Police Department, referred questions from The Post regarding Libby’s bail and his first court appearance to Quincy District Court.

This is not the first time a mask dispute has resulted in an MBTA passenger being arrested. When an MBTA bus driver asked passenger Daniel Rodriguez to wear a mask in November, the rider allegedly coughed in the official’s face, claimed he had the coronavirus and allegedly struck the driver with a chalk block. The 19-year-old was charged with assault and battery with a deadly weapon, according to police.

In July, the MBTA asked the public for help in identifying a woman who allegedly responded to a bus driver’s request to put on a mask by “smashing out the bus window.”

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