Monster death message displayed twice

[Ian]

Huge Cave, Refuse Pit
Also here: Yori, slime beast.
Obvious exits: southeast
The room is dimly lit
[HP=86/MA=10]:a slime beast
*Combat Engaged*
Yori moves to attack slime beast.
Yori moves to attack slime beast.
The slime beast slaps Yori for 16 damage!
Yori lashes slime beast for 16 damage!
Yori flays slime beast viciously!
Venom sears slime beast for 3 damage!
Yori whips slime beast for 21 damage!
Yori flays slime beast viciously!
Venom sears slime beast for 2 damage!
Yori lashes slime beast for 4 damage!
Yori flays slime beast viciously!
Venom sears slime beast for 3 damage!
You whap slime beast for 29 damage!
You whap slime beast for 30 damage!
You swipe at at slime beast!
You whap slime beast for 28 damage!
You whap slime beast for 24 damage!
Yori swings at at slime beast!
Yori lashes slime beast for 8 damage!
Yori flays slime beast viciously!
Venom sears slime beast for 2 damage!
The slime beast dissolves into a mass of reeking flesh.
You gain 125 experience.
*Combat Off*
Yori lashes slime beast for 4 damage!
The slime beast dissolves into a mass of reeking flesh.
Yori stops to rest.
[HP=86/MA=10]:

My best guess is because the monster was killed by a weapon spell, Yori still got another swing on it.  Most of the time it just dies normally.