The accused, Gaurav Kumar, had an argument with Mr Singh, who then slapped him. Enraged, the youth brutally killed the senior journalist with a kitchen knife and then strangulated his mother who was a witness to the crime, they said.
The veteran journalist and his 92-year-old mother were found murdered at their residence in 3B2 area of Mohali on September 23.
Addressing the media, Mohali SSP Kuldeep Singh Chahal claimed that the case had been cracked and the knife used in the crime, K J Singh's car that was stolen, a mobile phone, a wrist watch and a digital video recorder were recovered from Kumar, who is in his late 20s.
According to Mr Chahal, K J Singh and Kumar had a tiff after Singh questioned him for sitting suspiciously in a park close to his house on the night of the crime.
"Mr Singh had questioned the youth for sitting suspiciously in the park and slapped him, following which he killed the journalist and his mother, who was an eyewitness to her son's murder," the police official claimed.
Kumar had executed the brutal double murder alone, the SSP claimed.
Police claimed to have apprehended Kumar today afternoon from the airport road near Sohana Gurdwara when he was driving Mr Singh's car with a fake number plate.
Kumar was currently staying at Kajheri in Chandigarh, according to the police officials.
According to the post-mortem report, K J Singh had received multiple stab injuries, between 14 and 17, inflicted through a sharp-edged weapons while his mother was strangulated to death.