he accused, identified as Asif, was arrested on Monday.
A man allegedly threw his neighbour's five-year-old son and four-year-old daughter from the second floor of a building in Maharashtra's Thane district following which the boy died and the girl was severely injured, police said on Wednesday.
The incident took place in Devripada area of Mumbra township on Saturday and a probe was on to ascertain the exact motive behind the crime, they said.
The accused, identified as Asif, was arrested on Monday, an official from Mumbra police station said.
Asif and his wife, who do not have a child, were next door neighbours of the victims in the building.
The accused and his wife used to have frequent quarrels over petty issues. The accused's wife was a friend of the victims' mother and they used to talk frequently which he did not like, the official said.
On Saturday, the accused allegedly threw the two children from the second floor of the building where they were playing, he said.
The boy died on the spot and his sister suffered serious injuries. The girl, however, managed to go home and informed her father that their neighbour threw them from the building, the official said.
The body was sent to a government hospital for post-mortem.
Based on a complaint by the children's mother, the police arrested the accused and booked him under Indian Penal Code Sections 302 (murder) and 307 (attempt to murder), the official said.