Though he didn’t fire the fatal shot, the man charged with murdering 17-year-old Roniel Marc bears responsibility for his death because he chose to engage in a gunfight in the middle of a residential neighborhood, a Suffolk County prosecutor said in opening statements today.

Marc was shot to death after an altercation erupted at a Hyde Park barbecue on July 4, 2008, Assistant District Attorney Daniel Mulhern said. KEVIN LOUIS (D.O.B. 7/2/87) of Hyde Park is charged with second-degree murder and firearms offenses for his death.

“The guests at that barbecue were young and old, family and friends,” Mulhern said. “They prepared by bringing food and drinks, by sharing stories and listening to music. Mr. Louis prepared in a very different way – by arming himself with a loaded 9mm semiautomatic handgun.”

An argument broke out “between young men who lived in the neighborhood and Mr. Louis,” Mulhern said, and it soon escalated into a gunfight in which Marc and others participated along with Louis.

“The evidence will show you, and the ballistics will tell you, what happened that day,” Mulhern said, telling jurors that Louis travelled toward the firefight, not away from it.

“He had the intention of killing Mr. Marc that day, at any cost,” Mulhern said. “The law as the judge will give it to you doesn’t give Mr. Louis the benefit of being a bad shot. What the law calls this is murder.”

Jennifer Sears is the DA’s assigned victim-witness advocate. Louis is represented by attorney Christopher Belezos. Testimony is ongoing before Judge Frank Gaziano in courtroom 906 of Suffolk Superior Court.