BOSTON >> The former right-hand man of James "Whitey" Bulger testified today that he saw the alleged mobster open fire on a car and kill two men in 1982.

Kevin Weeks took the witness stand at Bulger’s racketeering trial and said he saw Bulger extort multiple businessmen and drug dealers for a cut of their profits.

Weeks said he first developed a friendship with Bulger in the 1970s while he was working as a bouncer at Triple O’s, a South Boston bar where Bulger did business as the leader of the Winter Hill Gang. Soon, he said, he was working as an enforcer, driving around South Boston and picking up cash from local bookmakers Bulger and his gang were extorting.

"Sometimes I’d beat somebody up," he said.

In May 1982, Weeks said, he went from being muscle to helping Bulger in a murder.

The target was Edward "Brian" Halloran, a man who Bulger had heard was cooperating with authorities.

"Brian Halloran was talking to the FBI about Jim Bulger and some murders," Weeks said.

Weeks said that after another Winter Hill member told Bulger he had spotted Halloran on a pay phone, Bulger drove to one of the gang’s hangouts in a "hit car." Bulger was wearing a wig and fake moustache, he said.

Bulger told him to drive to the waterfront and wait there, Weeks said. A short while later, Bulger drove up, with a man wearing a ski mask lying in the back seat. Weeks said the man waved to him, but he said he did not know for sure who it was.

Weeks said Bulger handed him a two-way radio, told him to watch Halloran in a restaurant, then let him know when Halloran was coming out.

Weeks said he told Bulger, "The balloon’s rising," as Halloran started to leave the restaurant, a reference to Halloran’s nickname, "Balloonhead." When Halloran walked outside, Weeks said he told Bulger, "The balloon’s in the air."

Halloran got into a blue Datsun driven by a friend, Michael Donahue.

Weeks said he saw Bulger pull up to the car.

"He slid across the front seat and he yelled out, ‘Brian!’ and he proceeded to start shooting," Weeks said.

The car Halloran and Donahue were in drifted across the road and hit something, Weeks said.

Halloran then got out of the car, and "Jim Bulger just started shooting right at him," Weeks said. "His body was bouncing on the ground."

Both Halloran and Donahue were killed. Weeks said he had never met Donahue, and he was not a target of the shooting.

Both Bulger and the person in the back seat fired at the car, Weeks said.

When he called Bulger later that night, Bulger said he was eating dinner with his girlfriend and urged him to "go get something to eat," Weeks said.

Donahue’s son Thomas, who has attended every day of the monthlong trial with his mother and two brothers, said hearing Weeks testify about the killing of his father had shaken his family.

"It tears you apart hearing the horrific story," he said.

Weeks, who was a close associate of Bulger’s for two decades, later became a government witness and eventually led authorities to the bodies of people who were allegedly killed by Bulger and the gang. He served five years in prison after pleading guilty to being an accessory to five murders.

Bulger stared straight ahead during much of Weeks’ testimony and only glanced at him occasionally.

Weeks also described how Bulger acquired a liquor store in South Boston. Prosecutors say Bulger forced Stephen Rakes to sell his liquor store to him in 1984 to use as a headquarters for his gang and as a source of "legitimate" income.

Weeks denied that the gang forced Rakes to sell the store, saying Rakes had agreed with an offer from Bulger to buy the store for $100,000. He said when they arrived at Rakes’ house to close the deal, Rakes said his wife didn’t want to sell the store and complained about the selling price.

"He was trying to shake us down," Weeks said.

At the time, Rakes’ two young daughters were in the room and Bulger was bouncing one of the girls on his lap, Weeks said. He said he pulled a gun out of his waistband and put it on the table. The girl on Bulger’s lap reached for the gun, Weeks said. Bulger then told him to put it away.

Weeks said Bulger told Rakes he couldn’t back out of the sale.

"At that point, we went through with the deal," he said.

"We didn’t go to him to buy the store. He came to us. It wasn’t your regular extortion," Weeks said.

Rakes, who was in the courtroom for Weeks’ testimony, later disputed his account and said he was forced to sell his store to Bulger.

"Kevin continues to lie, as usual, because that’s what he has to do," he said.

"My liquor store was never for sale — never, never, never."

In addition to the slayings of Halloran and Donahue, Weeks has testified previously that he was present for three other killings committed by Bulger.

Bulger, 83, is accused of playing a role in 19 killings while allegedly leading the Winter Hill Gang. He has pleaded not guilty.

Bulger fled Boston in 1994 and was one of the nation’s most wanted fugitives until he was captured in Santa Monica, Calif., in 2011.