The Marco Mangrove Murder Mystery

As I got closer, all I found was a bag that belonged to Ben Boss. This bag could very well change the course of my life, if what was inside was as implicating as I assumed. Ben Boss was a serial killer, a cold-blooded murderer whose tragic killing spree started in the Everglades of South Florida and ended in his standoff on the Goodland Bridge of Marco Island, within walking distance of where I found the bag. The bag itself was nothing special, just a khaki-colored camouflage zipper bag with heavyweight material and speckles of green that may have only appeared years after the thing was abandoned.
The evening sun beamed down at me as if telling me to leave the bag alone; being this far into the tangled mangrove trees, it seemed like nothing good could come of the situation. My possibly historic expedition into the unexplored mangroves of Marco Island had led me here, a parched mudflat that showed no sign of life if there was any at all. The smell rising from the flats penetrated my nose like a nail being hammered into a hesitant wall of hardwood. It resembled rotting eggs blended with what I assumed a dead body to smell like. Something about it almost made me wonder if one of the 13 poor women Ben Boss carved up in his days was left to rot in the hellish dead jungle I now found myself in.
Back to the bag, I thought, feeling a sense of urgency suddenly wash over me like a frigid winter surf.
It was as if Ben Boss himself had escaped his Alcatraz holding cell, swam through San Francisco Bay and made his way across the country to make me the first victim of his next killing spree. I turned my body around, tense, scanning the bleak horizon of gray mangroves grasping on to life for any threat. It was at this point I realized my feet had been slowly sinking into the muck that made this habitat its home, as when I tried to turn around, I physically couldn't and fell onto my hands in quite possibly the most awkward position a human being could find himself in.
From this position, my vision was upside-down, but the bag was in perfect view. Since it was partially unzipped already, I lowered myself down a little more to peer inside. I saw nothing distinguishable but the color red, fading to dark red and then black as my vision zoomed toward the back of the bag.
I pulled myself up with a struggle and wiped my gray muddy hands on my travel-worn khaki shorts after shaking what I could off. I pulled my feet up from the muck and took a few steps closer to the bag, now within grabbing distance. I took a deep breath, with millions of thoughts spiraling throughout my consciousness as I set a firm grasp on the top flap of the bag and the zipper handle. As I unzipped the rest of the bag, the red color I had just seen, however upside-down it was, now made itself more apparent as I realized the true nature of the object the bag was keeping safe.
A heart. Bloody and crimson red, the literal organ sat slightly off center in the bag, the sun near its death illuminating the surface. It is at this point I was made aware that my previous concerns about feeling watched and uncomfortable were reality. The heart was wet, and fresh blood dripped off of it. My limited medical knowledge made me assume that this must have been placed inside this bag less than a few hours ago.
A redtail hawk's cry resonated a few hundred feet overhead. It echoed inside my ears and traveled with haste along the land, intertwining itself among the somber mangrove trees and forever imprinting its sound upon the history here. I didn't even look up, nor flinch, nor move a muscle at all, because I was in shock and unsure of my next move.
The muck had now crawled up my legs and I was knee-deep. I struggled, using every muscle in my body that was relevant to pull my left leg first out of the muck. In my straining, I closed my eyes.

Then, my ears perceived an unpleasant sound: the sound of removing one's leg from thigh-deep muck.
I hadn't moved an inch; the sound came from behind me. My eyes opened and widened before I even knew what hit me.