(CNN) -- Images of a sky-blue car, its windows shattered by bullets, took center stage Monday at the trial of reputed mob boss James "Whitey" Bulger.
Bulger's onetime crime partner Kevin Weeks testified he was there the night Edward "Brian" Halloran was killed. He placed the gun squarely in Bulger's hands.
"Jim Bulger just kept shooting," said Weeks describing Halloran's writhing, bullet-ridden body as "bouncing off the ground." Halloran is one of 19 people Bulger is accused of killing during his 20-year reign of terror in South Boston. Bulger is on trial in federal court in Boston.
Rogue FBI agents had alerted Bulger that Halloran was going to cooperate against Bulger in a couple of killings.
Weeks testified that on May 11, 1982, while Halloran was at the Mullins Club, Bulger pulled up in his souped-up 1975 Chevy Malibu wearing a wig and floppy mustache to disguise himself as another crime associate.
Weeks watched Halloran inside the club. As he began to make his way out of the club, Weeks radioed Bulger, referring to Halloran as "balloon head," a nickname they used because "Halloran's head was so big."
"The balloon's rising," Weeks radioed Bulger as Halloran got up from his table. Then as he got to the door, "The balloon's in the air."
Weeks said he saw Bulger slide across the seat of the Chevy and call out to Halloran. Then, "Bulger started shooting."
Michael Donahue, a bartender, was driving his grandfather's blue car and had offered his neighbor a ride home. Donahue was killed instantly. But Halloran stumbled out alive, and Bulger kept firing, Weeks said. Donahue's widow and three sons have attended every day of the trial and virtually every hearing.
As police raced to the scene, Weeks said he calmly drove away, circling back to collect a hubcap, and then get something to eat because he was hungry.
Weeks said Bulger instructed him to get rid of the guns, which he threw into Marine Bay. He first removed a gun-stock because Bulger liked to use it.
Weeks was 27 years younger than Bulger when he began working for him. He described how he, Bulger, and crime partner Steven Flemmi would take long walks and talk about business. Prosecutors introduced several surveillance photos of the three men walking around Boston's Castle Island and even setting out lounge chairs in Columbia Park across from the liquor store that served as one of Bulger's "offices," all prevent anyone from listening.
"Everything I did, every business I had, Jim Bulger and Steve Flemmi were my partners always," said Weeks. Though Bulger and Weeks sat just six feet apart, Bulger ignored his old partner.
In one of the trial's rare light moments, prosecutor Brian Kelly showed Weeks a gun belonging to Bulger. As he lifted it, the handle came off and a spring popped out. Kelly recovered smiling, "I think that's the last gun we're going to show." Another light moment came when the prosecutor asked Weeks why he and Bulger had worn gloves while wiping down several guns, and Weeks laughed, "It's common sense among criminals."
Weeks wrote a book called "Brutal: The Untold Story of my Life inside Whitey Bulger's Irish Mob," in part to compensate victims as part of a civil suit against him. "My story was my only asset," said Weeks who served five years in prison and has testified for the government at five Bulger-related trials.