Suspended Chandigarh constable Basant Kumar alias Bunty, accused of two murders in Sonepat and one in Chandigarh, was nabbed by Haryana police in New Delhi in the wee hours of Sunday.
The police have recovered a carbine from him.
Kumar has confessed to the murder of Chandigarh inspector Sucha Singh, say police sources.
According to police sources, Kumar claimed that he killed Sucha Singh because he had identified him and could lead to his arrest.
Kumar was on the run for more than 50 days after the double murder of the husband and mother-in-law of a woman with whom he was having an affair in Sonepat.
He had come from Manali to Chandigarh and was to board a bus for Delhi on Friday night when he allegedly stabbed the cop a few metres away from the Sector 17 police station.
According to police, Kumar had been carrying about Rs 5 lakh cash, and stayed in Rishikesh, Shimla, Manali and other places while he was on the run.
Inspector Sucha Singh had earlier succumbed to the stab injuries at the Post-Graduate Institute of Medical Education and Research (PGIMER) in Chandigarh after the attack.
Basant Kumar had killed a 55-year-old woman, Roshni, and her son, Sandeep, 23, with his service weapon in Haryana's Sonipat district in April and absconded with a newly-wed woman, Sarita, with whom he had an affair. Sarita had been married to Sandeep for just three days when the constable attacked and killed the mother-son duo.
(With inputs from IANS)