Death Gun
Sinon shoots at Death Gun, but he dodges the bullet and then kills Pale Rider with his pistol. Death Gun then introduces himself and his gun to the spectators, finishing his monologue with a catchphrase used by PoH, the founder of Laughing Coffin. Meanwhile, Sinon attempts to find out Death Gun's name, but he was not shown on the satellite scan, thus Sinon assumes that he traveled through the battlefield underwater. She and Kirito then decide to follow Death Gun, eventually going to the Lost City. However, since they could not find him along the way, they look for him during the next scan. Seeing that two players, Sterben and Juushi X (銃士X, Jūshi X?), were present in the city, they decide to go after Juushi X, as his name sounded like Death Gun (死銃, Shijū?) backwards. During the scan, they find Juushi X at a stadium, while Sterben abruptly vanishes from the city. The two rush to the stadium and, after confirming that there was a sniper, decide to split up. However, as Sinon takes a sniping position, she is suddenly shot with a stun bullet. Death Gun, who is actually Sterben, appears and proclaims that he is going to kill her. Sinon tries to defend herself, but then sees that Sterben is carrying the Type 54 Black Star, the same weapon she used to kill the robber at the post office.
Aired 30/08/2014EP 9 - Death Gun

Sword Art Online II
One year after the SAO incident, Kirito is approached by Seijiro Kikuoka from Japan's Ministry of Internal Affairs and Communications Department "VR Division" with a rather peculiar request.
That was an investigation on the "Death Gun" incident that occurred in the gun and steel filled VRMMO called Gun Gale Online (GGO). "Players who are shot by a mysterious avatar with a jet black gun lose their lives even in the real world..." Failing to turn down Kikuoka's bizarre request, Kirito logs in to GGO even though he is not completely convinced that the virtual world could physically affect the real world.
Kirito wanders in an unfamiliar world in order to gain any clues about the "Death Gun." Then, a female sniper named Sinon who owns a gigantic "Hecate II" rifle extends Kirito a helping hand. With Sinon's help, Kirito decides to enter the "Bullet of Bullets," a large tournament to choose the most powerful gunner within the realm of GGO, in hopes to become the target of the "Death Gun" and make direct contact with the mysterious avatar.
(Source: Crunchyroll)