PARIS — A Massachusetts man, arrested along with his son after a fight early Thursday morning at a Waterford campground, told police that one of the victims punched his wife, and the attack on two Farmington men was retaliation.

John O’Brien, 40, and his son Jonathan O’Brien, 18, both of Billerica, Mass., were arrested at Papoose Pond Resort and Campground at 700 Norway Road early Thursday morning by Maine State Police Trooper Joseph Bureau. Both were charged with aggravated assault and assault. On Friday, both were released on $1,000 cash bail.

According to an affidavit by Bureau, William Powell, 43, of Farmington, had serious facial injuries and was flown by LifeFlight to Central Maine Medical Center in Lewiston. Michael Chapman, 46, of Farmington, had been knocked unconscious but had regained consciousness when Bureau arrived. Chapman was transported to Stephens Memorial Hospital in Norway.

According to the affidavit, John O’Brien told him that his children woke him and said the men at the next campsite had been aggressive and one punched John’s wife. Bureau said she had a bruise on her lip.

O’Brien said one of the men tried to punch him as he left his cabin. Bureau wrote there were signs of a fight halfway between the two campsites, and said he doubted the claim that the fight happened outside the cabin. John said he was the only one involved in the fight, Bureau wrote, but Bureau said he witnessed Jonathan O’Brien bragging about hitting Powell and Chapman.

Bureau wrote that neither John nor Jonathan showed any injuries, except to their knuckles. Because there were no other injuries on the O’Briens, and because signs of a fight showed they happened between the campsites, Bureau wrote that he doubted the O’Briens’ claim of self-defense and charged each with assault and aggravated assault. Powell and Chapman told Bureau that the O’Briens had attacked them.

Lt. Walter Grzyb of the Maine State Police said there may be more charges as state police investigate.

John and Jonathan O’Brien are set to appear in Oxford County Superior Court in Paris on Nov. 6.

[email protected]