Horrible loss, hoping for some input as to cause

[Will0W783]

Hi guys,

I took a really hard loss on Friday. My very first snake that I ever owned was a normal ball python named Saleen. I picked Saleen up at a local pet store 9 years ago. He was the one that really got me into this hobby and helped me realize how much I wanted to keep and work with snakes. I planned to always keep at least him, no matter where my life took me, for all his days.
Saleen was a typical 12-year-old male BP. He was fat, healthy and ate f/t medium rats. He'd occasionally go off of feed for the winter months, but he's done this every year.

He had been on another one of his picky eating spells, and hadn't fed for me in about 2 months (not unusual I thought). He was showing no signs of anything unusual, and I had him out for handling about once a month.

I had been in my reptile room on Thursday night and he was coiled under his hide. Friday when I came home from work, I was hit with an awful stench the moment I opened the house door. My snake room is at the end of a hallway on the ground level, as the house is on a hill, so you enter in the basement. I knew something was really wrong, and I ran right into my snake room. It stunk of death and foul water. I thought someone had regurgitated but I had last fed a week before....
when I got to Saleen's cage, he had his back half stretched out and braced against the cage wall. The front I'd say 1/3 of him was coiled up tightly around himself and smashed into the water dish. He was bloated. I put on gloves and removed him....his neck looked broken and the water in the dish was just bloody. There were at least 3 bite marks around his neck area.

All I can figure is something made him try to eat himself. He had a habit of coiling his food in his water dish, so I guess he went there with himself and drowned.

I'm heartbroken and really confused....I've never heard of a snake doing this before.

I'm also worried about my other snakes. Nothing new has come into that room in the last 2 months, and then it was only snakes that had been previously quarantined. Saleen has never been bred or housed with another snake, and I practice careful husbandry when feeding with tongs. I keep a bottle of 10% bleach water to spray off the tongs if a snake bites them, and then I rinse them before using them for the next snake, so I don't see how any contagions got into my collection. None of my other snakes is currently off feed or acting weird.

Does anyone have any input for me on what might have caused this? I'm terrified it's something I did wrong, or should have foreseen.