A teenage gang member brought a loaded .45 to a Chelsea strip club two years ago and “turned what should have been a barroom scuffle into an execution,” a Suffolk County prosecutor told a Superior Court jury this morning.

Charged with first-degree murder for the fatal shooting of 28-year-old Jeff Santiago, JESSE CAMACHO (D.O.B. 5/7/87) of East Boston opened fire at King Arthur’s Lounge in what Chief Trial Counsel Patrick M. Haggan called “a shooting rampage” that also left one of Santiago’s friends and a club employee with gunshot wounds to their legs in the early morning of Jan. 25, 2008.

After two full weeks of testimony, Haggan delivered his closing arguments this morning and told jurors that Santiago died “face down on a dirty, beer stained barroom floor” as his “cowardly killer” walked away trying to fire a gun he’d emptied after shooting seven separate shots.

Prosecutors say a fight broke out that night after a member of Santiago’s group approached a member of Camacho’s group and struck him with a bottle.

“This isn’t a group of close knit friends going to gang up on someone,” Haggan said. “This is one jerk.”

As a fistfight broke out, Camacho allegedly drew a gun and began shooting, hitting the three victims in the leg. Haggan railed against the notion that Camacho was defending himself or anyone else that morning, noting that Camacho hit Santiago in the leg and then calmly fired twice more at the wounded man as he “crawled for his life” amid the chaos that broke out.

“No one’s near him when he pulls out that gun,” Haggan said, pointing at a viewing screen depicting the spot “where Jesse Camacho put two bullets into Jeff Santiago as he lay helpless on the floor.”

Camacho fled Massachusetts shortly after the shooting. He was apprehended in Mexico City on Oct. 30, 2008 after extensive efforts by Chelsea Police, Massachusetts State Police, U.S. Marshals and Mexican Federales. He was rendited to Massachusetts on March 13, 2009.

After arguments, Judge Patrick Brady instructed jurors on the relevant law. If they do not reach a unanimous verdict today, they will return to courtroom 815 tomorrow morning.

Michael Schultz is the victim-witness advocate assigned to the case. The defendant is represented by attorney Willie Davis.