Since he put a round through his head I dont think that he would have cared If anyone was carring or not. Im sure he knew what the end result was going to be.
Actually, it's pretty much known in workplace violence prevention that these deranged spree killers will kill themselves at the first sign of armed resistance. They want to go out on their terms, not someone else's. Their worst fear is getting wounded and captured. A bullet in the brain is pretty painless compared to getting gutshot, patched up, paraded in front of the cameras, getting tried and convicted, then sent to prison where you share a cell with Bubba the top.