You are Dr Gordon Freeman, You and Alyx Vance are in an Apartment trying to get out of it, You Smash open a Civil Protection Unit's Head open with the crowbar, And blood spatters all over your face.

Alyx Vance: "Jeez Gordon.. You remind me not to mess w-"

You point your gun at her, shutting her up

Alyx Vance: "Gordon.. Dont shoot me.."

(Gordon Freeman is Mentally unstable, I figured that out due to the amount of His couleges dying, etc)