Police Commissioner Ram Singh said the main accused, Ranjit Singh Rana, was arrested from the border belt of Amritsar district Thursday morning along with another accused. Rana had been stalking assistant sub-inspector (ASI) Ravinder Pal Singh's daughter for the last few days.
Two other accused in the killing of Ravinder Pal are absconding, police said.
The ASI was allegedly shot dead by Rana and his accomplices after he objected to his daughter being subjected their harassment Wednesday.
The incident took place near the Chhehrata police station, on the outskirts of Amritsar city, 250 km from the state capital Chandigarh.
Ravinder Pal's daughter had complained that some youth used to harass her. The ASI objected to this and confronted the youth. Following an argument, Rana fired at him and his daughter and left them injured.
Eyewitnesses told the police later that Rana and his accomplices came back to the spot in a jeep later and shot at the ASI in the chest from close range.
Ravinder Pal was rushed to a private hospital where he was declared dead.
The Akali Dal expelled Rana, who is a general secretary of the district unit of the party.
District unit president U.S. Sandhu said that Rana was inducted into the party September this year and had now been expelled.