Dozens of uniformed and plain-clothes officers were in position on Pilkem Street in Yau Ma Tei before the 40-year-old man was brought to the scene in a police van on Tuesday afternoon.
Police said the victim, a 33-year-old man, was struck on the head with the hammer more than 10 times at around 2.20am on Sunday.
The victim, who operated a gambling den on Pilkem Street, died in hospital five hours later.
Officers on the same day arrested two men and three women in connection with the murder case.
The suspects include the 40-year-old alleged attacker and his girlfriend, both of whom are believed to have been part of the love triangle.
The other three were apprehended on suspicion of aiding and abetting the attacker.
At around 2.20pm on Tuesday, the murder suspect arrived at the scene on Pilkem Street under police escort. He was hooded and handcuffed to a chain around his waist, and wore a white long-sleeved shirt and a pair of slippers.
He was briefed while surrounded by officers, then brought to the block of flats where the gambling den operated before police closed it down on Sunday.
About 10 minutes later, the man was escorted out of the building and was seen carrying a hammer-shaped prop to simulate an attack on a life-size dummy as part of the filmed re-enactment.
The suspect was later brought back to the police vehicle and driven away.
The incident was one of two local murder cases that surfaced over the weekend.
On Sunday, police arrested a 43-year-old engineer on suspicion of strangling his 46-year-old girlfriend at her flat in Tsz Wan Shan. The force believed that case was also linked to a dispute over a love triangle.
The man was apprehended after his girlfriend, who was also a colleague, was found dead at the flat on Saturday evening.
According to the force, the pair had known each other for about 10 years and had been in a romantic relationship for around a year. A police source said the man suspected the woman had a new boyfriend.
The city recorded eight reports of homicide in the first five months of this year, three cases fewer than the 11 recorded in the same period in 2023.