Editor's note: This story contains graphic details that may be upsetting to some readers.

SPRINGFIELD -- After they killed three city men, Adam Lee Hall and his two co-defendants "gutted" the victims and then "chopped them up," according to David Casey.

Casey, 65, of Canaan, N.Y., said he was sitting in his truck in August 2011 when Hall described how he and two other men killed David Glasser, Robert Chadwell and Edward Frampton.

"I was dumbfounded in shock," Casey told jurors on Wednesday during Hall's murder trial in Hampden Superior Court.

In gruesome detail, Hall told Casey how he and two others killed the men in an undisclosed location.

Hall said the first time he tried to kill Glasser, he was holding him by the hair and pulled the trigger, but his gun jammed, Casey testified, and Glasser escaped and ran into the woods.

Casey said one of the other men went after Glasser, shot him and brought him back to Hall.

"He was kind of mad about that," Casey recalled Hall telling him.

"He's for me," Hall allegedly said before killing Glasser.

Glasser, whom Hall referred to as "the retard," begged for his life as Hall told him "I warned you what would happen if you testified against me," Casey said.

Hall also allegedly told Casey he had picked up Glasser's severed head and commented about how ugly he was.

Casey said the men stabbed Chadwell -- who Hall allegedly referred to by a racial slur -- and left him for dead but later found him slumped against a tree trunk moaning and calling for help.

"They killed him," Casey said.

He testified that Hall said it was hard to cut up Frampton because of his size.

Hall told Casey that one of the other men involved "was really into it" and "enjoyed torturing and cutting them up," according to his testimony.

Hall said it was raining heavily during the killings and that they drove home in their underwear afterward, according to Casey.

Hall allegedly told Casey it was satisfying to kill Glasser and that he "slept like a baby" afterward.

Casey is himself facing accessory charges for allegedly helping to bury the bodies.

He said Hall told him if he helped, "no harm would come" to Casey, his girlfriend, his sister or her boyfriend, Scott Langdon, who was a state's witness in another case involving Hall.

"My concern was for the safety of myself and my family," Casey said.

Casey called his friend Alan Pavoni, of Becket, at Hall's request to ask if Hall could keep a car there overnight and agreed to meet Hall there the next morning.

Casey said he drove around trying to decide what to do when Hall texted him and said he was at Pavoni's house. He said he went there because he was worried for the safety of his friends.

"The car with the bodies in it was there," he said.

When he got there, Hall introduced him to David Chalue, telling Casey he was a member of the Aryan Brotherhood and that in order to gain membership "you have to murder someone so you don't have to worry about him," Casey testified.

While there, Hall opened up the trunk of the Buick and said "they're starting to smell," Casey said.

William Ferry, who had been a tenant of Pavoni's in 2011, said he didn't smell anything coming from the car when Hall came to park it at Pavoni's residence.

Hall and Casey went over to the property of Daniel Cole, also in Becket, where Casey had been doing some work and dug an 8-foot-long trench in a secluded spot, Casey said.

After Casey replaced the bucket he used to dig with a larger one, Hall threw between six and eight garbage bags, which Casey described as "really sloppy," into his excavator bucket. Casey said he then dumped the bags into the hole and covered it over.

"Remember to keep your mouth shut. Even in jail I can make things happen," Hall allegedly told Casey after he was done.

"When I was digging that hole," Casey testified, "I didn't know if I was going to go in there too."

"You could get a violent reaction" from Hall if you did something he didn't like, he said, noting that Hall "has a reputation."

Casey said he was also frightened of Chalue who he described as having "Charlie Manson eyes."

He said after finishing the job, which he believed took about a half-hour, he began shaking and did not recall driving home.

Under cross-examination by Hall's attorney, Alan J. Black, Casey admitted that he initially lied to police during an interview and denied any involvement in the alleged crimes.

"I was afraid of retaliation from Hall, his friends and associates," Casey said.

He said he spoke with police on several occasions and admitted that over the course of the interviews he revealed more information. He admitted that several details of the alleged murders that he testified to on Wednesday hadn't been mentioned by him in police interviews.

"It's fair to say that cooperation was a theme throughout all the interviews?" asked Black. "Yes," Casey answered.

"This is your one shot, man. The guy that comes in is the guy who gets taken care of," an investigator told Casey during one of those interviews, according to testimony.

Casey said he was never promised anything for his cooperation, but hopes his testimony will help his case.

The trial resumes on Thursday.