Multiple witnesses in Hopkins County, Kentucky

Myself and a friend were bored one afternoon,so we decided to take his dad's small john boat and look around some creeks just a couple miles from his house.After putting in a time or two,we found one that kept going and stayed wide and deep enough to follow it for awhile.We only had paddles so we moved fairly quiet,i guess.After paddling for a few hours,and having to get out from time to time and drag the boat over beaver dams,it had became late afternoon and the sun started to go down.We had been talking and laughing the whole time,so we really weren't trying to be quiet.As we rounded a bend in the creek,we both saw a large piece of rock come flying out of the trees and land in the middle of the creek,making a big splash probably about 50 yards or so ahead of us.At the time,i was a police officer and was armed pretty much everywhere i went.That particular day we had been shooting trash like cans and bottles that we found alongside the roadway just up from where we put in at,so we were both armed.My friend immediately opened fire with warning shots in the general direction where the rocks came from, 5 or 6 shots as i was trying to turn the boat around.We normally wouldn't have freaked out like that but,it was the manner in which it occurred that scared us.The rock appeared to be bigger than anything either of us could've picked up,let alone throw like that.Another thing was,the height from which it came.Which was about 2 or 3 feet higher than i am tall from what i saw,and i am 6 foot one.Also,it was heavily wooded,flat,swampy creek bottoms so it didn't just fall from anywhere,and had the circumstances been where it could've fallen,it would'nt have landed in the middle of the creek.It would've just landed on the bank.After we got turned around and started paddling like crazy in the other back toward the truck,we didn't hear or see anything,but we still didn't waste any time.As it got darker,we started hearing footsteps up in the woods on our left.I say "footsteps" cause it didn't sound like any deer hooves that i had ever heard,it sounded like somebody large and heavy.When we'd stop paddling,it would stop walking.It would walk only when we paddled.This went on all the way to the point where we got close enough to the road to hear traffic going by,and it was all the way dark by then and had been for some time.Once we got to the road,we loaded up and got out of there in a hurry,not hearing anything else and very shaken.There were no houses for miles in either direction from where we parked other than my friend's house which was a few miles to the west and nothing to the east for roughly 5 miles.The property that the creek runs on is a 3000 acre tract of land that used to be a coal mine but had been shut down for several years.I tried to explain it away to myself but,it just didn't add up.I always figured,even if it had been some person large enough to throw a rock that size,they would've said something when my friend opened fire on em'.And,they sure wouldn't have followed us all the way back to the road for fear of being shot at again you would think.The swamp we were in runs across several counties, and is largely unpopulated in most parts so,who knows.