Growling in King County, Washington

My encounter took place along the white river,we were out hiking, the sun had gone down and we began hiking back under the moonlight, which had illuminated the trails nicely. As we walked down the trails through the woods I occationally heard the sounds of twigs and branches breaking as if somthing was moving through the trees and bushes about 10-15 feet off the side of the trail. I became greatly alarmed because whatever was creating the disturbance had been following us for quite a distance as i began paying more attention to the sounds of branches breaking i could hear that they were footstepts, just like the ones a human would make walking through the brush, i knew in my heart that it was a bipeadal creature at that point. still, we kept going but now i began to feel little bits of sticks and pebbles being thrown at me, as i turned my head to look behind me i saw a piece of stick come flying right at me from the bushes. at that same point my friend also turned and yelled at me to stop throwing stuff at him, i told him it was not me and i told him that whatever was throwning stuff was just beyond our sight off the side of the trail. we were all very scared. we stopped to rest along the river bank near the end of the trail, as we sat quietly i heard a low bass toned growl. judging from the sound it had to be a large creature, possibly a bear, but is a bear capable of walking on two feet for such an incredible distace and is a bear able to throw bits of sticks and pebbles with its paw? its from these facts that i belive we were stalked by a bigfoot.