Assassinate Boss Salvatore for Big Jesus Mordino

You can do this a number of ways, the easiest 3 are (in order of difficulty) Super Stimpaks, Stealing the Oxygen Tank, Guns blazing.

use super stimpaks to make him explode into a bloody form of his self.

Steal the Oxygen Tank and watch him die from what else...

Guns blazing go cap the poor man's ass.