FALL RIVER — Two New Bedford men sped up to a Mercedes on New Year's Eve 2015 and fired six gunshots, killing one and wounding the driver in what a prosecutor described Tuesday as "an ambush."

Aaron Gant Jr., a 24-year-old New Bedford man, was shot in the back of the head and killed in the shooting about 7:20 p.m. Dec. 31, 2015, at Grinnell Street near Pleasant Street, New Bedford, prosecutor Bob DiGiantomasso said in Superior Court. The driver, Aaron Watkins, was wounded in the arm.

The shots came from a Ford Fusion driven by Angel Acevedo with shooter Aaron Bookman, who was in the front passenger seat, the prosecutor said.

Bookman, 25, and Acevedo, 26, are charged with murder, carrying an illegal firearm and assault and battery by means of a firearm and are being tried together in Superior Court.

The motive stemmed from simmering tensions between young people in the West End and the South End of New Bedford during 2015 and was in retaliation for earlier shootings of Acevedo and his girlfriend and the house where Bookman's ex-girlfriend lived and Bookman sometimes stayed, he said.

The New Year's Eve shooting was the culmination of a plan by Acevedo and Bookman that began on Christmas Eve 2015. "This was the pair's idea for street justice," DiGiantomasso said.

Acevedo was shot in the leg on May 31, 2015, and he and his girlfriend were both shot on Oct. 21, 2015, the prosecutor said. In the Oct. 21 shooting, Acevedo was shot in the face and his girlfriend was shot in the foot.

Acevedo knew who shot him, but never told police, the prosecutor said. However, Acevedo did mention to hospital staff that he knew who was responsible.

On Christmas Eve 2015, Acevedo "secretly left" New Bedford and drove to Maine in violation of his probation, which prohibited him from leaving the Commonwealth of Massachusetts, DiGiantomasso said. In Maine, he visited a friend, who rented the Ford Fusion in Saco.

Acevedo provided the car for the New Year's Eve shooting and Bookman provided the firearm, which has not been recovered by police, the prosecutor said.

Bookman and Acevedo, self-described "cousins," were from the West End of New Bedford and had "a long-standing hatred" of some in the city's South End, he said. "It was the West End's turn and they didn't miss," DiGiantomasso said.

There is surveillance video of Bookman and Acevedo traveling from the North End of New Bedford to the South End, a 14-minute drive, to where the fatal shooting occurred on that New Year's Eve, he said.

When Watkins stopped the red Mercedes he was driving at 112 Pleasant St. to drop off one of the passengers, Acevedo sped up the Ford Fusion and pulled behind the Mercedes and Bookman fired six gunshots in 3.4 seconds before speeding off, the prosecutor said.

"The shooting executed Aaron Gant Jr. and grazed the arm of Watkins," he said.

Acevedo "ditched" the rental car at the Carter Brooks School in New Bedford and then went to Shaw's Supermarket in Dartmouth, he said. He and his girlfriend then went to a New Year's Eve party and early the next morning he picked up the rental car and drove to Seekonk, where he stayed overnight. The following day he drove back to Maine "to swap out" the Ford Fusion.

"Again on probation, shouldn't be out of state," DiGiantomasso said. Police later located the rental car in Maine and found gunshot residue on the windshield.

There were no shell casings found at the scene and police believe the murder weapon was a revolver, which does not discharge shell casings, the prosecutor said. Bookman's ex-girlfriend in Florida saw Bookman with a revolver.

John J. Connors of Fall River, defense attorney for Acevedo, asked jurors to keep an open mind and let the facts decide the case.

"We're not deciding a case on emotions. We're not deciding a case on a story. We're deciding a case on the facts," Connors said.

Bookman's attorney, Jack Atwood of Plymouth, declined to make an opening statement at the start of the trial.

Judge Renee P. Dupuis is presiding at the trial, which is expected to be lengthy with estimates ranging from anywhere from 2 1/2 weeks to 4 weeks. The jury includes nine women and six men and will be reduced to 12 when deliberations begin.

Follow Curt Brown on Twitter @CurtBrown_SCT