Damon Sehra allegedly told Amjad Khan: “I know you – you rushed me,” Mr Andrew Smith QC, prosecuting, told Wolverhampton Crown Court.
The victim was then grabbed from behind by Sehra's uncle Derek Brennan, aged 32, and floored by a hard punch to the face from Sehra, continued the prosecutor.
The pair started to kick and stamp on 32-year-old Mr Khan as he lay stunned and helpless on the living room floor and was hit over the head with an empty bottle and a toy by the younger man, the court heard.
The brutal attack was launched at the maisonette home of Sehra’s mother Lisa in Yardley Close, Bristnall Fields, Oldbury, minutes after midnight on June 8 last year, the jury was told.
Her son and brother – who had both been drinking beer and brandy and smoking cannabis – had joined forces around an hour earlier to beat up a 15-year-old youth in an unrelated incident which took place nearby, it was said.
They then made an unexpected visit to Ms Sehra’s flat, who had not seen either of them for some time, minutes before her friend Mr Khan arrived, maintained Mr Smith.
He continued: “After the door was opened by Ms Sehra he went to shake hands with the two men.
"Damon Sehra said: ‘I know you – you rushed me.’”
After the beating both climbed through the living room window and fled, taking the black pouch-style bag of the victim with them, while Ms Sehra frantically called 999 just eight minutes after he arrived.
She told the operator: “I am locked in my flat. Someone is going to die. Get an ambulance, please help me. My son and brother are beating him up in my flat. They trod on his face – oh God I can’t look at him. They kicked and jumped me.”
Mr Khan, who lived in Handsworth, suffered a fatal cardiac arrest as a result of the battering, the jury heard.
Police, paramedics and a doctor joined forces to give him artificial respiration and managed to restart his heart.
He was taken to Birmingham’s Queen Elizabeth Hospital where doctors found the brain injury triggered by the cardiac arrest could not be treated and five days later he was certified dead having not recovered consciousness.
Mr Smith told the jury: “You can be sure that this was a direct result of the unlawful attack on him. There is no doubt these complications led ultimately to his death.”
Sehra, of no fixed address, denies murder but pleads guilty to manslaughter on the grounds of diminished responsibility.
He further pleads not guilty to attempting to cause grievous bodily harm to the 15-year-old but admits assaulting him.
Brennan, of Halesowen Road, Netherton, denies all the alleged offences.
The case continues.