Usually, she only lets you shoot one at a time; then you will need to stun the boss again. Quickly reload a powerful weapon such as a shotgun (or machine gun) to have a . nbsp; the ability to kill several monsters at a time. You can also get extra energy by killing another boss on the way to the ghost boss, but this is more difficult. However, if you can’t kill him while he is standing still, you should consider stunning him. If you shoot him while he is running, you will kill him faster. You can also use it to stun his colleague in case she follows him. You will need to avoid the bosses.