Fallout: Equestria - Dazed and Confused

I wake up in a daze.

Realizing I am on my back, I lazily roll over onto my stomach, shaking my head with my forehooves in an attempt to rid myself of my grogginess. I blink a few times, my vision finally clearing up enough in order to take in the environment surrounding me.

My eyes widen in shock as I pan across the scene. There are no less than half a dozen ponies around me, all of them dead. Not one of them is even twitching. Blood is smeared along the walls and in myriad pools across the floor. One pony, a yellow unicorn with a teal mane and tail, is even hanged from the ceiling, her neck and face purpled from oxygen deprivation. Her body gently sways in the musty, metallic-smelling air as I wince and cast my eyes to the floor in front of my face. I spot a small, torn photograph of the same hanging unicorn, but she is smiling and among friends... perhaps even family. Next to it is an empty syringe and a few bullet casings. I sigh in a defeated manner and attempt to stand, realizing said attempt is all too futile as my legs buckle beneath my weight.

Taking another look around the room, trying (and failing) to ignore the bodies scattered around the room, I notice a door slightly ajar. Hobbling my way over to it, wincing in pain with every step, I peek into the crack to take a look around. Inside it is pitch black, but after some waiting I adjust to the low-light and am able to see that it was, in fact, the door to the outside. A gentle and moist breeze blows by as I look up to the clouds, barely visible in the darkness. I am finally able to stand with some effort, taking the time to look at myself in a puddle nearby.

I see a monster staring back. My face is covered in gashes and scars, and my blue coat is bloody and matted. My barding is similarly covered in blood, a simple leather outfit now ruined. Looking down at my legs, I realize why it was so hard to stand. Both of my back legs are bowing in odd directions and are broken. It dawns on me that I likely don't feel the pain due to the empty syringe I'd spotted earlier – it was likely filled with Med-X and was used on me shortly before I passed out. The only real question left unanswered here is:

What the fuck happened?