Report 113: Son and friend find footprints. Later something stalks them along riverbank, incident retold by his father

Although I, nor my boys have actually seen a bigfoot, they have seen strong evidence of one. About 1975, my son and his friend found large tracks in fresh snow south of Galesburg, KS.  They followed these tracks for about a half mile until they stopped under an old railroad trestle. Sometime later, they were checking limb lines about 12:30 AM in their boat in the same area. The night was very dark and although they had a flashlight, all it would reveal was the immediate brush along the creek. As they paddled along, they kept hearing something in the brush which they assumed was a deer. A few minutes later, a huge rock came flying downward in front of their boat and hit the water. Whatever it was had to be either human, or a human type of creature. It is unlikely to have been a person since that side of the creek is avoided because of its inaccessability and very heavy brush.