Kessler, who's active in gun rights circles and started an armed group that critics call a private militia, posted videos of himself shooting borough-owned automatic weapons and cursing liberals and others who he said want to erode the constitutional right to bear arms.
Kessler said the council's decision was "no surprise" in light of the incendiary videos. "We knew it was coming," he said.
A closed-door disciplinary hearing earlier in the day had dwelled on unrelated allegations, including that Kessler improperly used a state-administered program to buy discounted tires for his personal vehicle, failed to submit required crime data and made derogatory comments about borough officials.
Kessler's attorney, Joseph Nahas, said the charges were trumped up to conceal the town's intent to fire Kessler over the videos. He said after the vote he'll request a public hearing at which both sides can call witnesses, as is Kessler's right under due process rules. The council would then have to vote a second time to fire Kessler.
Kessler told reporters that he had been an excellent police chief and had nothing to apologize for. He said he'd broken no laws: "None. I'd be in handcuffs."
"My message was to wake up the people who are independents," he said, "to say, 'We've had enough and something needs to change, because we're in bad shape all around. Not only here in this little town but across the nation. It's a mess.'"
Kessler's pro-gun videos have garnered hundreds of thousands of views online. He acknowledges they are inflammatory but says they're designed to draw attention to the erosion of Second Amendment and other constitutional rights.
Mayor Mary Lou Hannon had said she found the police chief's language offensive.
Council members declined to comment after Thursday night's vote.
Kessler, a former coal miner, has spoken at gun rights rallies and created a website on which he seeks recruits for the Constitution Security Force, whose stated mission is to defend the constitution and the country from tyranny.
Gun rights activists had traveled to the community of about 800 people, in Schuylkill County in eastern Pennsylvania's anthracite coal country, to show support for Kessler, and most of them displayed weapons.
Constitution Security Force member Bob Gardner traveled from Philadelphia.
"Mark has gotten railroaded," said Gardner, who carried a semi-automatic AK-47. "He was exercising his First Amendment rights by backing it up with his Second Amendment rights."
In January, Kessler drafted a resolution the borough adopted that calls for nullifying any federal, state or local regulations that infringe on the Second Amendment.