LOWELL — A 71-year-old Marine Corps veteran from Tewksbury is being held on $5,000 cash bail as he faces charges he was drunk during a road-rage incident in Billerica that allegedly led to both he and another man brandishing guns.

But an attorney for Roger Buonanno, of 14 Boisvert Road, Tewksbury, says his client wasn’t drunk, and displayed his legally owned handgun only once he felt threatened by three other men who were involved in the incident.

“He’s a solid member of the community and an honorably discharged veteran,” attorney Steven Rappaport said. “He displayed his gun when he felt threatened.”

The incident began Saturday, about 4:30 p.m., when Buonanno was driving on Cambridge Street in Burlington, according to police.

Assistant District Attorney Andrew Ineson said another vehicle cut Buonanno off, which prompted Buonanno to follow that vehicle as the incident entered Billerica.

Buonanno followed that vehicle to a home on Lindsay Road in Billerica, according to police.

Rappaport said Buonanno was on the phone with police at the time, reporting that the other vehicle was being driven erratically and nearly caused an accident, and that he was trying to get the other vehicle’s license plate number.

Police said dispatchers repeatedly told Buonanno not to follow the vehicle, but that he did so anyway.

Ineson said Buonanno pulled up to the driveway of the home where the other vehicle stopped, and that he then pointed a handgun at three men in the driveway. Ineson said a witness told police one of the men in the driveway also pulled a handgun.

But Rappaport said Buonanno only displayed his gun once he felt threatened by three large men in the driveway, one of whom was also armed.

“He didn’t point it at anybody,” Rappaport said. “He merely made it clear that he had a gun.”

Officers soon arrived at the scene and took Buonanno into custody after determining he was drunk, according to police. Police said there were several beers inside Buonanno’s vehicle. Ineson said Buonanno has prior drunken driving convictions in Concord and Woburn.

Rappaport disputes that Buonanno was drunk

“Why would he call the police if he was drunk,” Rappaport asked.

Both Buonanno and the other man, who was not identified in court, had licenses to carry firearms, but have since had their guns confiscated by police, according to Rappaport.

Police said they are also seeking charges against the other gun owner, who will be summonsed to court to face a charge of assault with a dangerous weapon (handgun). That man’s name was not immediately released since he was not arrested at the scene.

Judge Stacey Fortes granted Ineson’s request to redact that man’s name, the names of the other two men involved, and the names of all witnesses from publicly available police reports.

Rappaport objected to the redactions, saying they were “silly” since his client already knows the location where the men live.

Rappaport said Buonanno is retired, a father of two, and that he has no history of failing to appear in court. He said Buonanno’s previous drunken driving convictions occurred over two decades ago. He asked Fortes to release his client on personal recognizance.

Buonanno is charged with third-offense operating under the influence, carrying a firearm while intoxicated, possession of a firearm during the commission of a felony, and three counts of assault with a dangerous weapon (handgun).

Fortes granted Ineson’s request for $5,000 cash bail and ordered that, if Buonanno posts bail, he must stay away from and have no contact with witnesses or alleged victims, must possess no guns or dangerous weapons, not drive without a license, and consume no alcohol and submit to random screens.

Buonanno is due back in Lowell District Court on May 16 for a probable-cause hearing.

Follow Robert Mills on Twitter @Robert_Mills.