Chota Hafiz, prime accused in the blast, died in an encounter in the state's Kishtwar district. The National Investigation Agency, which probes terrorism cases, had put a reward of Rs 10 lakh on him.
Another accused, Amir, was gunned down by the police earlier.
Investigators had found that the September 2011 blast outside a gate of the Delhi High Court was planned in Kishtwar. An email claiming responsibility for the attack was traced to a cyber cafe in Kishtwar. Explosives were provided by local militants of the Hizbul Mujahideen.