There is only need to fire one shot: the one that impacts the BG right between the eyes. His/her/its warning is the sound of the gunshot.
Weatherby Vanguard in 7mm Rem Mag
Remington Model 572 Pumpmaster
Remington Model 11-87 12 guage
Remington Model 870 Express 12 Gauge w/18.5 in. barrel
And plenty of ammo for all of them