Guild Wars 2

Can someone please tell me what killed me, hitting me twice, as sown at the following picture? I was fighting some undead, when out of nowhere I got 2 big hits and went down.
Is this a bug?

Possibly a risen plague carrier?
http://wiki.guildwars2.com/wiki/Risen_Plague_Carrier

Or maybe the corpse of a risen chicken; even though that would be odd for that side of the map since I don’t recall ever seeing them over there.

Those are my guesses.

Often these plague carriers fail to render. So you get killed by an invisible enemy. The damage they do is also absurd. And if the game doesn’t know what killed us, how are we supposed to know?