SHO Loni Kotwali Avdhesh Pratap Singh said acting on a tip-off, the trio -- Nafees, Jaaul and Asrat -- were nabbed from Khazoori Pushta road.
One 9mm pistol and its three cartridges, two .315 caliber country made pistols with four live cartridges and a motorbike were recovered from their possession.
Those arrested were the main culprits, while nine others, accused of hatching the criminal conspiracy, were still at large, Singh said.
Fifty-year-old Shamshad, a resident Pavi Sadakpur village, was killed on August 2 when he was going to his office on his motor cycle.