Right before you start Honest Hearts in the cave, you can talk to Ricky, (the guy in the vault suit) and he will claim that he killed a Brotherhood of Steel Paladin and the Courier tells him that he's full of [censored] and then Ricky explains that he killed him by shooting him in the eyeslit part of the helmet (trying to make his story more believable) and if you have Power Armor Training the Courier discredits that claim by revealing that even the "eyeslits of T-series Power Armor are bullet-proof, [so you're lying]."
You can look at that and come to your own conclusions.