Screaming or howling in Shasta County, California

I was on a houseboat vacation with my family at Shasta Lake when I was 13. We had put our houseboat to shore in a secluded cove that branched off of the main lake. I went on a walk alone along the shore, and then followed a near-dry creek bed that came down out of the nearby woods to the lake. I had followed the creek bed for about a mile when I came upon two sets of footprints in the mud along the creek bed. Both looked human-like, with five-toes. One set was about a size 14, the other about a size 9, comparing them to my own foot at the time. They were very wide prints, and appeared neary flat-footed. I was curious, though I hadn't made the Bigfoot connection yet. It had seemed odd to me that someone would have been barefoot this far into the woods. The tracks came out of the nearby woods, down to the creek bed, and they then followed the bed for a while away from the lake and into the deeper wooded region. After a few hundred yards, they turned up a slight grade and into the woods on the opposite side from which they started. Another thing that made me suspicious of the prints were that they had crossed the rocky creek bed, which was filled with sharp, shale-like stones. It seemed to me that it would have been a very painful experience for any human to walk those rocks barefoot. I noted that the larger prints were set wider apart than the smaller prints. Still not making a BF connection, I went back to the houseboat and said nothing to my family. That night my brother and I were in our sleeping bags on top of the houseboat, still parked in the same spot. We were both drifting off to sleep when we both heard a very loud scream. It sounded like it was fairly far away. At first, I thought it had been a woman screaming. Then I hear the scream again. It started off sounding like a baby beginning to wail, but then got louder and more high-pitched like a woman's voice in full scream. It seemed resonant, like it was coming out of a hollow tube. As it ended, it dropped down into a low gargle-like growl. Both screams lasted maybe three seconds each. It was then that I put the footprints and scream together in my head. Though my brother heard the screams also, we didn't really talk about it. My brother buried his head in his bag, while I tried to stay awake to listen for more sounds. After a while I had fallen asleep, and awoke the next morning to find that my family had already moved the houseboat out of the cove as I slept, so I didn't get to go back to investigate the footprints again. I did not tell my family about my Bigfoot suspicians, but my brother did mention to me later that he heard a "bear" walking along the shore that night, near where the houseboat was aground. He said he heard heavy footsteps, heavy breathing, and some grunting. I'm not so sure I buy the "bear" theory.