Randomly getting kill effects without killing anything

As a Berserker with a Showstopper mace, I have two effects that have a chance of happening when I kill an enemy: the Rampage skill, and Meteor Strike that has a 10% of happening when I skill an enemy with Showstopper.

The weird thing is, they've been randomly triggering. I'll be just walking through a dungeon, minding my own business, when suddenly a meteor falls from the sky and hits an area near me. I've also have Rampage randomly trigger without any obvious cause.

This is not caused by my pet or a summon killing something. It's happened in cases where I have no summons active, and can see what my pet has done for the last few seconds.

Is this a bug? Am I missing something?

This seems to be caused by stepping on bugs triggering kill effects.

I noticed that there are bugs that randomly run around on the ground, and if you step on one, it makes a splat sound and makes a blood effect.

Just now, I heard the splat sound, saw the blood, and had a meteor hit the exact spot that I had stepped on the bug.

This seems to suggest that this phenomenon is caused by killing bugs having the ability to trigger killing effects.

I'm not sure if this can be used for any strategic purpose, but I'm glad that I finally came to a reasonable conclusion.