Sinon fails to kill Death Gun with her long distance shot. Pale Rider ends up getting killed, presumably in real life, too. When Sinon tries to find out Death Gun’s name in satellite scan, the name is nowhere to be found.
Kirito and Sinon decide to follow Death Gun before he kill other players. Since Pale Rider can’t be the Death Gun (as he has clearly became a victim), then there are 2 names that can be Death Gun: Steven and Musketeer X.
From satellite scan, they find Musketeer X’s location at a stadium. Kirito goes there with Sinon as backup from distance. She’s a sniper anyway.
Suddenly, Sinon is down with a stun bullet and Death Gun is ready to kill her. Sinon manages to reach her gun, but she can’t shoot after seeing that the “Death” Gun is actually a Type 54 Black Star Gun, exactly the same type as the one she grabbed from the robber 5 years ago. The gun that caused her trauma.