A man accused of murdering a student at a New Year's Eve party in Brighton allegedly described the victim's last breath and said he had been thrown out a window, a trial has heard.
Gregory Hawley also allegedly told a witness that the 24-year-old victim, Billy Henham, had also been 'butt naked'.
The witness, Donna Malloy, told a jury on Tuesday that Hawley "said it with no emotion in his eyes."
She continued: He is sick. That is someone's son, someone's kid."
Mr Henham was beaten unconscious in what was described to the court a 'sustained and significant' assault before being thrown unconscious over roof terrace railings.
Hawley, 28, is one of four men on trial accused of the murder of Mr Henham at a squat in Brighton on New Year's Day last year.
Lamech Gordon-Carew, 20, Dushane Meikle, 27, and Alize Spence, 18, are also jointly accused of the murder.
A jury heard Mr Hengam could have been alive for up to an hour after the violent attack.
His battered, lifeless body was eventually discovered by police on January 2.
He was found lying on his back on a low-level recess area at the rear of a former office block, hotel and restaurant complex, with traces of disinfectant in his hair.
A court heard he had suffered 11 rib fractures, extensive bruising to his scalp, face, and neck, cuts and a brain injury. All were consistent with being punched, kicked and stamped on.
Mr Henham, who lived with his parents in Henfield, West Sussex, had also been struck with a broken wooden stair spindle.
Two deleted photos of his body - one partially clothed and one naked - were later found on Meikle's phone.
A jury heard Mr Henham, who was studying at Ravensbourne University in London, had spent Christmas with his family but wanted to see in the New Year in a 'lively atmosphere'.
After going to a nightclub and then an off-licence, he ended up at the party in the disused building in North Street sometime after 4.30am on January 1, but was dead within a few hours, Maidstone Crown Court, in Kent, was told.
Ms Malloy, from Brighton, was among people squatting at the property.
Giving evidence, she admitted her memory was hazy from drug-taking but described seeing Hawley with 'cleaning equipment' on the morning of January 1.
"I remember there was hardly anyone in the squat. I saw Greg with the cleaning equipment. He had J-cloths and a spray bottle," she told the jury.
"That's when he turned round to say 'We were going to burn the house down with you in it but we like you and you need to go. There's a body upstairs and we need to clean it'.
"I thought he was joking. I thought it was b***s**t, to be fair. I was more interested in running upstairs and getting my drugs. Stuff like that goes over my head and I don't listen to people."
Ms Malloy said she then moved with her partner to a second squat nearby, where the alleged boasting continued.
She told the court there was talk of Mr Henham being 'battered' and it 'started to make sense' what Hawley had said to her earlier.
Choking back tears Ms Malloy added: "What I can't get out of my head was him saying the kid was gasping his last breath, he was butt naked and they threw him out of the window.
"He said it with no emotion in his eyes. He is sick. That is someone's son, someone's kid."
Gordon-Carew, of Hampton; Hawley, of no fixed address; Meikle, of Hove; and Spence, of Northolt, all deny murder.
At the start of their trial, prosecutor James Mulholland QC said that although the motive for Mr Henham's alleged murder was 'unclear', all four defendants were being accused of participating in a joint attack.
"The prosecution case is that each defendant either joined in the physical attack upon William Henham or deliberately helped or encouraged one or more of the others to do so," he told the trial."
"Each intended in doing so that he be caused at least really serious injury and they are all guilty of murder."
The trial continues.