Blayn Jiggetts—the defendant in the Kirkland shooting case who allegedly brought and loaded the gun that killed Justin Cosby—began his testimony yesterday in the trial of alleged shooter Jabrai Jordan Copney.

Jiggetts recounted in detail the events surrounding the May 18, 2009 shooting of Cambridge resident Cosby, as Jiggetts answered questions from Assistant District Attorney Daniel J. Bennett ’85 in rapid succession.

According to Jiggetts, Copney had intended to rob Cosby of his marijuana and asked Jiggetts to bring a gun along because Cosby “was a street kid.”

Jiggetts, who assisted Copney in the alleged armed robbery of two Yale students in New York in late 2008, turned to his longtime friend Jason Aquino for the weapon. Aquino gave Jiggetts a 9-millimeter semiautomatic in exchange for Aquino’s share of the robbery, according to Jiggetts.

The original plan was to make the exchange on May 17, but Jiggetts said he was “having second thoughts about the robbery and didn’t want to go through with it,” Jiggetts noted in court yesterday.

In his testimony, Jiggetts said that he and Aquino met Copney at the McDonald’s in South Station to plan the robbery. Jiggetts would pull the firearm out and demand the marijuana, and Copney would take the drugs.

The trio met Copney’s girlfriend and former Harvard College student Brittany J. Smith in her dorm room in Lowell House where Copney asked Jiggetts to load the gun, Jiggetts said yesterday.

The three men left Lowell for Kirkland House and searched the entryways of the Annex for a secluded, quiet area using Smith’s Harvard University ID card. They settled on the art room in the basement of J-entryway before making arrangements with Cosby to meet there, Jiggetts said.

Copney and Aquino, who thought they could better impersonate Harvard students, met Cosby in his car. The four were reunited in the basement of J-entryway about 10 minutes later, according to Jiggetts.

As planned, Jiggetts pulled the firearm out of his bookbag and raised it to Cosby, demanding the marijuana that they had agreed to purchase. Cosby waved the marijuana in front of Jiggetts but did not let Jiggetts pull it away from him. This exchange carried on a few times before Copney tapped Jiggetts on the shoulder, and Jiggetts handed the firearm to him.

Jiggetts told Copney to let Cosby go, he said yesterday in court.

“In my eyes, it wasn’t worth it,” Jiggetts said. “We were trying to take a small amount of marijuana, and it was turning into something different.”

As Cosby pushed past Jiggetts, Jiggetts heard a gunshot, then two more. He rejoined Copney and watched Cosby run through the gate of the Annex. The three men left Kirkland House for Smith’s room, where they waited for Smith to call a cab.

The four then took the cab to South Station and left for New York where Aquino’s girlfriend was waiting for them, according to Jiggetts.

Jiggetts said that he and Copney discussed what happened.