"Kill mercenaries using firearms" is an optional objective in the mission Johnson's Errand
Kill 10 of them with firearms to complete this optional objective.
After the cutscene ends, press Y to shoot the mercenary up above.
Note that ranged weapons require ammunition to shoot. The amount of ammunition remaining is displayed by the weapon indicator.
Press RB to reload.
The icon in the lower right of the screen shows how long your weapon will take to reload. If you use the spare muskets on the racks, you won't have to reload.
Loot the dead bandit.
Dialog[edit]
Get into position/ But WAIT for me to take the first shot.
