third option, bit of a glitch, but do the following!! talk to father Elija via the computer in the vault, make sure you explore all the options when talking to him, then get him to come down to the vault, the door then opens, run out and turn right, there
is a set of steps and a blue forcefield barrier, at the bottom of the steps drop any c4 you have, then walk up to the barrier and try walking through it, when Elija arrives he uses a pip boy to teleport into the vault, when he does you swap places, and you
are on the other side of the barrier, save your game, then blow up the c4 and kill him, then exit via the lift, then reload, the game but don't blow him up and leave via the lift to trap him!!!! that way you get the 2 achievements, also you can empty the vault
of EVERYTHING, and still make it to the barrier before Elija gets there!!!