Noooo, What's Happened Now?

[Madjonny]

I had a thread last week explaining how I had high nitrites in the water but no ammonia, iv been changing water and doing tests every day...
Everything has been back to the correct levels for a few days now, everyone acting normal, until this guy yesterday spent all day on his own hovering in amongst the plants...
Now this morning I wake up to find my platy dead.

After taking him out and changing water I examined him, and his insides are hanging out next to or out of his gills... What could have happened?

Here are a couple of pictures I took when examining...

 

[TallTree01]

Could he have been attacked?

 

[Madjonny]

The only species in the tank are:

Betta
Platy
Swordtail
Black widow tetra
Garra rufa

I know bettas can attack, but why would it attack a platy?
The rest are peaceful fish...

 

[BerryAttack]

well ... that sucks... 
 
could have been that the platy got cut on a plastic plant, and then led to this... 
or just a wild guess maybe the garra rufa sucked on him... because they are used in spas to remove dead skin off the body... and boom surprise
or maybe just a freak accident