Guild Wars 2

I was just looking over my weapon master achievements, and I noticed I had over 1000 kills with a sword….but I have never used a sword. I also have kills with Rifle, axe, speargun, pistol, and hammer….Also weapons I have never used. Can anyone explain this, and how I could have gotten these never using said weapons? thanks.

Certain environmental and siege weapons count.

For instance, I received a weapon master achievement for Staff (I use S/D) while doing a storyline mission where I was firing the tank. Any kill with a “siege” effect from that tank counted as a Staff kill.