its simple, say me and you are fighting and im using this gun.
you come within range and i fire.
a long beam connects from my gun to your player doing a specific amount of health per second, aslong as i keep my finger on shoot, it will stay connected to you unless you go out of range or another player comes closer, which would make the chain switch from you to him.
D shot i think could shoot a charged beam that if it hits a player, splits and hits an additional 2 more players.