35-year-old Muneer was arrested in Ghaziabad near Delhi. The police say he had nine pistols.
A former student of the Aligarh Muslim University, he is allegedly involved in two other murder cases.
Mr Ahmad, 45, was driving back to Delhi from a family wedding on April 3 when two men on a bike stopped his Wagon R car and shot him 24 times. His wife Farzana Khatoon was also killed. Their children, aged 14 and 12, who were told by their father to duck, survived the attack.