Surendra Chauhan, 32, was shot at by three bike-borne miscreants on August 2 when he was out for a morning walk.
Police said the attack was masterminded by one Qazi Mohammad Asif, who hired four youths to kill Chauhan.
Qazi, a resident of Shahin Bagh in Delhi, is into real estate business, Sub-Inspector Rakesh said, adding, he had a rivalry with Chauhan.
Qazi along with the three youths - Babloo, Rahul alias Amit, Robin - were arrested today and produced in court, the SI said.