Muneer, who masterminded the murder, was arrested by the STF from Noida, he said.
Motorcycle-borne assailants had pumped 24 bullets into 45-year-old Ahmad and four into his wife Farzana Khatoon in April last.
The accused followed Ahmad, who was returning home to Sahaspur village, Bijnor district with his family after attending his niece's wedding in another village on the intervening night of April 2 and 3.
The attackers overtook his vehicle at Sahaspur village and Muneer allegedly fired at Ahmed and his wife.
Farzana succumbed to injuries at AIIMS 10 days after the incident.
So far four persons had been arrested by the police in connection with the NIA officer's murder.
Earlier, police arrested Rizvan, Tanzeem, Rehan and Zainul in this connection.
Uttar Pradesh Police had claimed to have solved the case by arresting Rehan, who is the nephew of Ahmad's brother-in-law, along with Zainul.
After the arrests, the police had contended that domestic dispute was the motive behind the crime.