The five accused, including three women, have been booked but no arrest has been made so far, he said.
The victim, Sunny Walmiki, 28, who worked at a private establishment in Ulhasnagar town here, had apparently levelled some allegations recently against the wife of one of the accused which had enraged them, Hill Line police inspector M G Waghmare said.
On June 7, when Mr Walmiki was sleeping at his house in Thane district's Ambernath town after lunch, the son of one of the accused came there and called him outside.
Mr Walmiki's wife Mitta, 26, told the boy that her husband was sleeping and she would send him outside after he gets up.
Later, the five accused came to Walmiki's house, forcibly woke him up and allegedly beat him up severely in front of Mitta, who is four months' pregnant, and the couple's minor son, Mr Waghmare said.
Mr Walmiki, who was seriously injured in the attack, was rushed to a hospital where doctors declared him brought dead, he said.
The deceased's wife, in her written complaint sent to police yesterday, said she made all possible attempts to save his life but in vain.
She also said that while the accused were attacking her husband, she locked her son in another room to save him. Based on the complaint, the Hill Line police last evening registered offences against the five persons under various sections of the Indian Penal Code, the inspector said.