I'm having trouble getting the La Longue Carabine without killing Corporal Sterling, I've tried shooting it off of him and then holstering my weapon, but they continue to attack me, are there any other methods I could use?

Get a silenced sniper rifle, find a way to be hidden while still having him in view, kill him in one shot, profit?

I found this-----"1) Save the game. 2) Use a stealth boy and steal his ammo. 3) Punch him and he will holster his gun and put up his fists; disengage combat(hold X). 4) Save the game again. 5) With the stealth boy still active you can now steal the gun. The stealing success rate on this character seems to be around 33% so the whole process should only take a few minutes. Hope this helps."