[@iHxzardx] Can you give me a link to the rifle? Like a picture or a website selling it? I want to see what you're talking about, because I don't believe any amount of air pressure can match a gunpowder charge, especially on skin and bone penetration.

You also said that he killed four people with (I assume) the rifle. Pretty sure that, considering how long it takes to pressurize an air rifle, and that air rifles have absolutely crap long-distance range, you could maybe kill two of them.