Harpreet Singh Grewal, son of Keetu's brother, was arrested during a security checking near Billaspur village here this morning when he was coming from Barnala, SSP Moga Surjit Singh Grewal said.
A rifle used in the crime was also recovered from him, the SSP said.
Another accused, Harpal Singh, also surrendered before police today, he said.
Earlier, police had nabbed Harpreet's brother Gurpreet Singh, and another accused Kulwant Singh on November 6 from Badhi Kalan.
Former Barnala MLA and SAD leader Keetu was shot dead on October 29 near the entrance gate of his house at his native Bilaspur village here allegedly by five persons, including three of his nephews.
One of the three nephews is still at large.
