After activating Execution Mode, Kid's guns reconstruct into two metal-plated cannons, forming over Kid's arm to make them literally metal Shinigami designed arm-cannons. In the anime, it is depicted in a way that they transform via a pink substance which is most likely the color of Liz and Patty's soul wavelength.
The technique consists of Kid charging his and his weapon partners' Soul Wavelength (namely the Black Needle Wavelength in the anime), then firing a ball of pure wavelength from the cannons leaving nothing but a plume of skull shaped smoke. The extent of the blast is so powerful that the resulting recoil, is enough to blow Kid several inches back, as shown in the anime.As they go through the resonance process, three black 'needles' sprout from back of Kid's upper-arms.
Kid first displayed Death Cannon against his fight with Soul and Black☆Star. He used it at a resonance rate of 0.3%, which was enough to leave them scathed. Later on, Kid then used it again in his fight against Free at a resonance rate of 1.8%, but didn't damage Free physically since he was unknowingly fighting against an illusion.During the fight for BREW, Kid used Death Cannon against Mosquito in his form from 100 years ago, and it was powerful enough to separate Mosquito's arms from his body with the help of Black☆Star using his Shadow☆Star: Pull and Slash cutting them. It then left Mosquito unable to move, only balancing by his long nose digging into the ground to keep him up. At this stage, Kid was in Chain Resonance with team Maka and team Black☆Star along with his own weapon partners, which allowed his soul resonance rate to increase to 2.4%, his highest soul resonance rate used along with Death Cannon.