A pair of alleged gang members shot 13-year-old Luis Gerena, Jr., dead after plotting to shoot the first person they saw who looked like a member of a rival group, a Suffolk County homicide prosecutor said in opening statements today.

DARRELL RODRGUES (D.O.B. 5/24/90) of Roxbury is charged with first-degree murder for his role in Gerena’s 2007 slaying. He is additionally charged with unlawful possession of the .32 caliber semiautomatic handgun used to kill him, assault and battery on a witness in the case, and intimidation of a witness. Today marked the first day of his trial in Suffolk Superior Court.

“January 12, 2007, started out like any other winter day for Luis Gerena,” Assistant District Attorney Mark Hallal told a panel of jurors, recounting the subway ride he took from Jackson Square, near the home he shared with his grandmother, to the Clarence Edwards Middle School in Charlestown. Later that evening, he went to visit his girlfriend and took the subway home again.

“At the same time, this defendant, Darrell Rodrigues, and his best friend started to make a decision – a conscious, deliberate decision to rob and shoot the first kid they saw who resembled a Heath Street kid.”

Rodrigues and NURUDEEN ALABI (D.O.B. 11/6/89) were gang members associated with the Academy Homes housing development, Hallal said, and had a longstanding rivalry with another group affiliated with the Heath Street development. Alabi will be tried separately at a later date.

“Luis Gerena … had nothing to do with any gang,” Hallal said. The boy “was simply coming home from school and visiting friends.”

Gerena left Jackson Square station and was approaching the nearby basketball courts on his way home when Rodrigues and Alabi arrived in a car driven by a friend of theirs, Hallal said.

“They set upon him,” Hallal said. “They surrounded him.”

In the moments that followed, five bullets were fired “at close range” into the boy’s body, causing injuries that would kill Gerena at Boston Medical Center a short time later. After killing him, Hallal said, the pair stole his phone.

A few days after Gerena’s death, the prosecutor said, Rodrigues and Alabi confronted a young woman who had been in the car that drove them to Jackson Square. After picking her up in that vehicle, Alabi allegedly pointed a gun at her from the front seat while Rodrigues got her in a headlock and forced her face toward the gun.

“Just do it,” Rodrigues allegedly said.

Katherine Moran is the DA’s assigned victim-witness advocate. Attorney Jack Courtney represents Rodrigues. Prosecution testimony will begin this afternoon after jurors take a view of the crime scene.