The Hamas explosives expert who was killed in an explosion in the Gaza Strip on Sunday developed an armor-piercing rocket for the organization’s armed wing, Iz al-Din al-Qassam, the group said.

Mohammed al-Kuka, 37, died Sunday of wounds he suffered in an explosion, Hamas’ military wing reported. The circumstances of the explosion were not clear, but Palestinian reports said the blast took place in a warehouse where explosive devices were manufactured.

A senior military wing commander said Saturday that al-Kuka was heading the development of an armor-piercing rocket, which was revealed by the group in a video.

In the video, the military wing said the rocket was an improved version of a Russian anti-tank rocket, which was used for the first time during the 2014 Gaza war with Israel.

The rocket is described as similar to an RPG with an armor-piercing tandem charge and a range of 500 meters. The group said the new rocket proved effective during the violent conflict.