BOSTON (CBS) – A driver who’s accused of stabbing another driver during a road rage fueled confrontation was released on $500 bail Tuesday. Colum Flaherty, 62 of Quincy, pleaded not guilty at his arraignment in Boston Municipal Court, saying he acted in self defense.

It all began Monday afternoon after a rear-end crash on Morrissey Boulevard.

State police say Flaherty and another driver stopped to exchange information after the fender-bender, when a third driver became irate over the traffic tie-up.

According to police, 54-year old Michael McDevitt of Quincy pulled up to the scene yelling expletives. “Get out of my way! I have to pick up my kid,” he reportedly yelled.

State Police say McDevitt then blocked Flaherty’s vehicle, got out of his own car and began pounding on the driver’s side window of Flaherty’s SUV. Then, according to court records, McDevitt pulled open Flaherty’s car door, and began hitting the 62-year old in the face and neck.

That’s when Flaherty grabbed a 3-inch pocket knife, and stabbed McDevitt in the arm.

“He’s had major surgery recently, had bypass surgery. He was scared to death and he took out his knife, warned the man, the man continued to hit him and then he stabbed him,” Flaherty’s attorney Jose Vincenty told WBZ-TV Tuesday.

WBZ New Radio’s Ed Walsh speaks with Flaherty’s attorney, Jose Vincenty.

WBZ News Radio’s Lana Jones talks to state police about what happened.

Flaherty was arrested on a charge of assault and battery by means of a dangerous weapon.

McDevitt was treated for minor injuries. He is expected to be summonsed to court at a later date to face charges of his own.

“He is expected to face a count of assault and battery on a person over 60 and other offenses for allegedly striking Flaherty in the confrontation that preceded the stabbing,” Wark said in a statement Tuesday afternoon.

WBZ-TV’s Bill Shields and WBZ News Radio’s Lana Jones contributed to this report.